The invention relates to an imaging element comprising at least one imaging layer wherein said imaging layer comprises photosensitive silver halide layer comprising dye forming couplers, a transparent polymer pragmatic sheet below said at least one imaging layer, an adhesive layer below said pragmatic sheet, and a black carrier sheet below said adhesive layer.

The invention relates to packaging materials. In a preferred form it relates to the use of clear silver halide pressure sensitive labels for the printing of text, graphics, and images applied to packaging material.
Pressure sensitive labels applied are applied to packages to build brand awareness, show the contents of the package, convey a quality message regarding the contents of a package, and supply consumer information such as directions on product use, or an ingredient listing of the contents. Prior art packaging labels are typically ink printed utilizing flexography or gravure cylinders. The three types of information applied to a pressure sensitive label are text, graphic, and images. Some packages only require one type of information, while other packages require more than one type of information.
Prior art labels that are applied to packages consist of a pragmatic sheet material, a pressure sensitive adhesive, and a carrier sheet. The label substrate consisting of the pragmatic sheet, pressure sensitive adhesive, and carrier sheet are typically laminated and then printed utilizing a variety of nonphotographic printing methods. After printing, the labels are generally protected by an over laminate material or a protective coating. The completed label consisting of a protection layer, printed information, pragmatic sheet, pressure sensitive adhesive, and carrier sheet material is applied to packages utilizing high speed labeling equipment.
Clear labels are currently utilized in packaging to provide a xe2x80x9cno label lookxe2x80x9d. Typically, prior art clear labels comprise flexo printed ink on a transparent polymer substrate. The transparent polymer substrate, when applied to the package, allows the native color of the package and contents of the package to visually interact with the printed inks. Clear labels are also useful in allowing the consumer to observe the contents of the package when used in combination with clear packages such as clear water bottles and glass beverage bottles.
Flexography is an offset letterpress technique where the printing plates are made from rubber or photopolymers. The printing on pressure sensitive label is accomplished by the transfer of ink from the raised surface of the printing plate to the surface of the material being printed. The rotogravure method of printing uses a print cylinder with thousands of tiny cells which are below the surface of the printing cylinder. The ink is transferred from the cells when the print cylinder is brought into contact with the pressure sensitive label at the impression roll. Printing inks for flexography or rotogravure include solvent based inks, water based inks, and radiation cured inks. While rotogravure and flexography printing do provide acceptable image quality for most current applications, these two printing methods require expensive and time-consuming preparation of print cylinders or printing plates which make printing jobs of less than 100,000 units expensive. Setup cost and the cost of the cylinders or printing plates is typically depreciated over the size of the print job.
Recently, digital printing has become a viable method for the printing of information on packages. The term xe2x80x9cdigital printingxe2x80x9d refers to the electronic digital characters or electronic digital images that can be printed by an electronic output device capable of translating digital information. The two main digital printing technologies are inkjet and electrophotography.
The introduction of piezo impulse drop-on-demand (DOD) and thermal DOD inkjet printers in the early 1980""s provided inkjet printing systems. These early printers were very slow, and the ink jet nozzles often clogged. In the 1990""s Hewlett Packard introduced the first monochrome inkjet printer, and, shortly thereafter the introduction of color, wide format ink jet printers enabled businesses to enter the graphic arts market. Today a number of different inkjet technologies are being used for packaging, desktop, industrial, commercial, photographic, and textile applications.
In piezo technology, a piezo crystal is electrically stimulated to create pressure waves, which eject ink from the ink chamber. The ink can be electrically charged and deflected in a potential field, allowing the different characters to be created. More recent developments have introduced DOD multiple jets that utilize conductive piezo ceramic material which, when charged, increases the pressure in the channel and forces a drop of ink from the end of the nozzle. This allows for very small droplets of ink to form and be delivered at high speed at very high resolution, approximately 1,000 dpi printing.
Until recently, the use of color pigments in jet inks was uncommon. However, this is changing rapidly. Submicron pigments were developed in Japan for ink jet applications. Use of pigments allows for more temperature resistant inks required for thermal ink jet printers and laminations. Pigmented water-based jet inks are commercially available, and UV-curable jet inks are in development. Pigmented inks have greater lightfastness and water-resistance.
Digital ink jet printing has the potential to revolutionize the printing industry by making short-run, color print jobs more economical. However, the next commercial stage will require significant improvements in ink jet technology; the major hurdle remaining is to improve print speed. Part of this problem is the limitation of the amount of data the printer can handle rapidly. The more complex the design, the slower the printing process. Right now they are about 10 times slower than comparable digital electrostatic printers.
Electrophotography was invented in the 1930""s by Chester Carlson.
By the early 1970""s, the development of an electrophotographic color copier was being investigated by many companies. The technology for producing color copiers was already in place, but the market was not. It would take many more years until customer demand for color copies would create the necessary incentive to develop suitable electrostatic color copiers. By the late 1970""s a few companies were using fax machines that could scan a document, reduce the images to electronic signals, send them out over the telephone wire and, using another fax machine, retrieve the electronic signals and print the original image using heat-sensitive papers to produce a printed copy.
In 1993 Indigo and Xeikon introduced commercial digital printing machines targeted on short-run markets that were dominated by sheet-fed lithographic printers. Elimination of intermediate steps associated with negatives and plates used in offset printing provides faster turnaround and better customer service. These digital presses share some of the characteristics of traditional xerography but use very specialized inks. Unlike inks for conventional photocopiers, these inks are made with very small particle size components in the range of 1 xcexcm. Dry toners used in xerography are typically 8-10 xcexcm in size.
In 1995 Indigo introduced the Ominus press designed for printing flexible packaging products. The Ominus uses a digital offset color process called One Shot Color that has six colors. A key improvement has been the use of a special white Electro ink for transparent substrates. The Ominus web-fed digital printing system allows printing of various substrates using an offset cylinder that transfers the color image to the substrate. In principle, this allows perfect register regardless of the substrate being printed; paper, film, and metal can be printed by this process. This digital printing system is based on an electrophotographic process where the electrostatic image is created on the surface of a photoconductor by first charging the photoconductor by charge corona and exposing the photoconductive surface to a light source in image fashion.
The charged electrostatic latent image is then developed using ink containing an opposite charge to that on the image. This part of the process is similar to that of electrostatic toners associated with photocopying machines. The latent charged electrostatic image formed on the photoconductor surface is developed by means of electrophoretic transfer of the liquid toner. This electrostatic toner image is then transferred to a hot blanket, which coalesces the toner and maintains it in a tacky state until it is transferred to the substrate, which cools the ink and produces a tack-free print.
Electro inks typically comprise mineral oil and volatile organic compounds. They are designed so that the thermoplastic resin will fuse at elevated temperatures. In the actual printing process, the resin coalesces and the inks are transferred to the substrate. There is no need to heat the ink to dry it. The ink is deposited on the substrate essentially dry, although it becomes tack-free as it cools and reaches room temperature.
For several decades a magnetic digital technology called xe2x80x9cmagnetographyxe2x80x9d has been under development. This process involves creating electrical images on a magnetic cylinder and using magnetic toners as inks to create the image. The potential advantage of this technology lies in its high press speed. Tests have shown speeds of 200 meters per minute. Although these magnetic digital printers are limited to black-and-white copy, developments of color magnetic inks would make this high-speed digital technology economically feasible. The key to its growth will be further development of the VHSM (very high speed magnetic) drum and the color magnetic inks.
Within the magnetic digital arena, a hybrid system called magnetolithography has been built and tested on narrow web and short-run applications developed by Nipson Printing Systems in Belfort, France. The technology appears to provide high resolution, and tests have been conducted using a silicon-based, high density, magnetographic head. Much more work is necessary in the ink development to bring this system to a competitive position relative to inkjet or electrophotography. However, the fact that it has high speed printing potential makes it an attractive alternate for packaging applications in which today""s ink jet and electrophotography technologies are lagging. Photographic materials have been known for use as prints for preserving memories for special events such as birthdays and vacations. They also have been utilized for large display materials utilized in advertising. These materials have been known as high quality products that are costly and somewhat delicate, as they would be easily defaced by abrasion, water, or bending. Photographs are traditionally placed in frames, photo albums, and behind protective materials in view of their fragile and delicate nature, as well as their value. They are considered luxury items for the consumers to preserve a record of important events in their lives. They also have been considered as expensive display materials for advertising. In view of their status as luxury items, they have not been utilized in other areas of commerce.
The use of a clear substrate in a photographic material can present many problems. Scratch resistance of the photographic emulsion is an important consideration. Optical degradation due to light wave reflection off the backing material is an important problem to solve. Optical interference during printing and during densitometric evaluation is another problem to solve. In some applications, this opaque printing may be desirable on a clear label to set the text off from the product inside. An example of this may be a product with an abundance of texture, such as peanuts or candy. Providing a combination of opacity and transparency with a photographic media requires a novel approach.
Typically pressure sensitive labels are supplied with a carrier sheet web material that allows the pressure sensitive label to be transported though the printing process and converting process while protecting the adhesive. Prior art carrier sheet materials typically comprise a coated paper or a thin polymer carrier sheet onto which a release coating is subsequently provided. Carrier sheet materials typically utilized in the pressure sensitive label are not suitable for a photographic label. Problems such as photographic reactivity with the light sensitive layers, lack of stiffness of the carrier sheet, and edge penetration of processing chemistry into the paper used as a carrier sheet prevent typical polymer and paper carrier sheets from being utilized for photographic pressure sensitive labels. Further, in U.S. Pat. No. 5,866,282 (Bourdelais et al), the need for a white reflecting layer under the emulsion for a high quality silver halide image formulation is proposed. Printing a silver halide image without a white reflecting layer will result in a loss of printing speed, image sharpness and poor quality test.
There is a need for clear pressure sensitive labels for application to packages that have photographic quality and, at the same time, economical for short runs. There is a further need for the printing of the clear silver halide labels without a loss in image quality and text quality. There is a further need to prevent optical interference during densitometric evaluation of the photographically printed and processed silver halide label media.
There is also a need to provide a combination of opaque dyes and transparent dyes in clear pressure sensitive labels for application to packages that are have photographic quality and, at the same time, economical for short runs.
It is an object of the invention to provide higher quality images to packaging materials.
It is a further object to provide clear silver halide imaging labels that have bright and sharp images.
It is a further object to provide a clear silver halide label material that is substantially free from optical interference during densitometric evaluation.
It is another object to provide a printing method that is economical for smaller printing jobs less than 100,000 images.
It is a further object to provide a method for providing a clear label material that features a combination of transparent photographic dyes and opaque printing inks.
These and other objects of the invention are accomplished by an imaging element comprising at least one imaging layer wherein said imaging layer comprises photosensitive silver halide layer comprising dye forming couplers, a transparent polymer pragmatic sheet below said at least one imaging layer, an adhesive layer below said pragmatic sheet, a black carrier sheet below said adhesive layer, and a method by which opaque inks can be placed beneath transparent photographic dyes.
The invention has numerous advantages over prior practices in the art. Recently there has been a trend in the marketing of mass consumer items to try to localize the marketing to separately approach smaller groups. These groups may be regional, ethnic, gender, age, or special interest differentiated. In order to approach these different groups, there is a need to provide packaging that is specifically directed to these groups. As discussed above, the traditional packaging materials are generally suited for very long runs of material, and to form shorter runs or to provide rapid changes in packaging is impossible or very expensive. We have found silver halide based photographic materials that are suitable for packaging uses. Further, recently there has become available high-speed photoprocessing apparatus suitable for short to long continuous runs of material. The combination of low-cost packaging-suitable photographic material with the processing apparatus available for high-speed short and long runs of material has resulted in the opportunity for silver halide material to be utilized in packaging materials. Silver halide materials that have properties such as low cost and the ability to flex and bend has resulted in materials suitable for packaging.
The utilization of the thin, flexible, and tough silver halide materials results in a packaging material having many superior properties. The transparent invention materials are capable of having brighter, sharper, and higher color images than anything presently available in packaging. The packaging materials of the invention have a depth of image unsurpassed by existing packaging materials. The packaging materials of the invention may provide a variety of packing materials that are suitable pressure sensitive labeling of packages such as shampoo bottles, perfume bottles, and film boxes. The packaging materials of the invention, while having the advantage of superior image, are available on thin transparent base materials which are low in cost while providing superior opacity and strength. The packaging materials of the invention, as they may be imaged by flash optical exposure or digital printing, have the ability to be formed in short runs and to be rapidly switched from one image to the next without delay.
The transparent silver halide labels provide unsurpassed image quality and provide the popular xe2x80x9cno label lookxe2x80x9d. Further, because the dye used to form the silver halide images are semi-transparent, the contents of the package can interact with the silver halide image in a way that grabs the attention of a consumer. An example is a silver halide image that has the same color as the contents of a clear package. As the contents of the package are emptied, a separate image or message is revealed. For example, messages such as xe2x80x9cBuy Morexe2x80x9d or xe2x80x9cThank You for Your Businessxe2x80x9d can be revealed as the contents of a soft drink bottle are emptied. Since prior art clear labels are typically printed with pigmented inks, the interaction with the contents of the package is difficult. Another application is on products that are delicate in nature, such as hand lotion or liquid soaps, or have a high sophistication, such as perfumes, colognes, and fine wines with light coloration. In applications such as these, the use of a label with transparent dyes may be particularly advantageous. A photographic pressure sensitive clear label could provide this unique look, be high in quality, and at the same time be economical for short runs.
Packages with transparent sides can create unique looks when combined with transparent labels, especially when the combined viewing of two or more labels can provide images that are a synthesis of the individual images on the component labels. At its most basic level, two labels of different colors when viewed together can create a third color. For example, combining cyan and magenta colors provide the color blue. This effect could be used in combination with the contents of the package. For example, as blue raspberry soda is consumed, a secret message can be revealed which is viewable only by aligning the front and back labels and drinking the contents of the bottle. The combination of complementary colors, such as blue and yellow, can create black, which can eradicate part of the image on a front or back label for a special effect.
Packages with transparent sides can create unique looks when treated with a combination of transparent and opaque labels. For example, a clear front label can be effectively used on a transparent package in combination with a back label which has information printed on an opaque reflective surface oriented towards the front label. This package would provide the dual advantages of allowing the contents of the package and the information on the back label to be viewed through the front label. Also, the opaque back label would eliminate distracting elements behind the package, such as other packages, from being viewed. Lastly, the other side of the opaque back label can provide other information regarding the product, such as ingredients, instructions for use, or website information.
The silver halide label material of the invention is provided with a carrier material that can be efficiently transported through a digital or optical printer that contains edge guiding equipment, as prior art carrier sheet are not stiff enough to allow for edge guidance. Further, the carrier sheet allows for efficient control of static, known in the art to cause premature exposure of the silver halide imaging layers. The label material of the invention also allows for efficient image processing, as the imaging chemistry is not absorbed and carried into subsequent processes such as in prior paper carrier sheet materials. The carrier sheet of the invention provides antihalation on the liner material, preventing unwanted secondary exposure of the of the silver halide imaging layers thereby significantly improving image quality and text quality compared to using prior art carrier sheet materials. Antihalation refers to the mitigation of light halation, which is an optical spreading of light around a point source. If the spread is far enough, a halo can be formed around the light. Halation leads to optical degradation.
The silver halide label materials of the invention allow packages to be rapidly designed and brought to market. For instance, significant events in sports or entertainment may be practically instantly brought to market as a digital image may be immediately flash exposed onto silver halide pressure sensitive labels and utilized within moments from the time of the event. This is in contrast to typical photogravure or flexographic imaging where lead times for pressure sensitive labels are typically several weeks. Further, the quality of the silver halide formed image lends itself to collectable images formed as a part of packaging much better than previous images which were of lower quality and were less desirable for collecting. This is an important consideration for short run promotional items where the quality of the product reflects on the quality of the organization sponsoring the promotion. Finally, the regional customization of images is rapidly possible.
The ability to rapidly change packaging also would find use in the need to provide regional labeling with different languages and marketing themes in different countries. Further, different countries have different legal labeling requirements as to content. For instance, alcoholic beverages such as wine and beer are subject to a wide variety of regional and national variations in labeling requirements. Wines manufactured in France may have long delays in shipping out of France due to the wait for national labeling in other countries. Photographic images also would be particularly desirable for a premium products such as fine wines, perfumes, and chocolates, as they would be of high quality and reflect the high quality of the product in the package.
The invention provides a printing method that is economically viable when printing short runs as the cost of printing plates or printing cylinders are avoided. The use of silver halide images applied to a package ensures the highest image quality currently available compared to the common, but lower quality six-color rotogravure printed images. Further, because the yellow, magenta, and cyan layers contain gelatin interlayers, the silver halide images appear to have depth compared to ink jet or electrophotographic images which appear flat and lifeless. Silver halide image layers have also been optimized to accurately replicate flesh tones, providing superior images of people compared to alternate prior art digital imaging technologies.
In some cases it is desirable to not only have transparent photographic dyes with depth, but to back these dyes with an opaque reflective layer. This can be important on packages in which the contents have enough fine detail in their appearance to interfere with the perception of fine detail in the label. For example, fine text on a clear label may not be readable when backed by non-associated detail in the package or the contents of the package. Or the color of the text may not be enough to set it off from a background color. In these cases it would be advantageous to create an opaque backdrop in those areas of the label where it is important to differentiate the detail in the label from the detail in the package. This can be accomplished by printing the image onto the clear photographic label media via optical or digital light exposure, photographically processing said label to form the image, separating said label from said carrier sheet, and then printing opaque inks on the other side of the substrate from the transparent dyes, thus printing on top of the previously applied adhesive. Any of the conventional printing methods could be used for this application. Most common would be a flexographic printing process, whereby the carrier sheet is stripped from the label during the process, the back side of the label is printed with opaque inks, and then the carrier sheet is reapplied in-process after the printing has been completed.
Another method to create the combination of transparent and opaque dyes on a clear media is to design the media such that the adhesive remains adhered to the carrier sheet and not to the label. In this case, opaque inks could be applied to the other side of the substrate from the transparent dyes without printing on top of the previously applied adhesive. This would open the range of printing inks and ink coverages that could be used in this fashion. More adhesive would then be applied to the back side of the label on top of the printed opaque inks either in-line with printing, or in a post-printing operation such as during application of the label to the package, just prior to adhering the label to the package.
Silver halide image technology can simultaneously print text, graphics, and photographic quality images on the pressure sensitive label. Since the silver halide imaging layers of the invention are both optically and digitally compatible, text, graphics, and images can be printed using known digital printing equipment such as lasers and CRT printers. Because the silver halide system is digitally compatible, each package can contain different data enabling customization of individual packages without the extra expense of printing plates or cylinders. Further, printing digital files allows the files to be transported using electronic data transfer technology such as the internet, thus reducing the cycle time to apply printing to a package. Silver halide imaging layers can be digitally exposed with a laser or CRT at speeds greater than 75 meters per minute allowing competitive printing speeds compared to current ink jet or electrophotographic printing engines. These and other advantages will be apparent from the detailed description below.
The terms as used herein, xe2x80x9ctopxe2x80x9d, xe2x80x9cupperxe2x80x9d, xe2x80x9cemulsion sidexe2x80x9d, and xe2x80x9cfacexe2x80x9d mean the side or toward the side of a photographic packaging label bearing the imaging layers. The term environmental protection layer means the layer applied to the post processed imaging layers. The terms xe2x80x9cpragmatic sheetxe2x80x9d, xe2x80x9cpragmatic sheetxe2x80x9d and xe2x80x9csubstratexe2x80x9d mean the material to which the silver halide layers are applied. The terms xe2x80x9cbottomxe2x80x9d, xe2x80x9clower sidexe2x80x9d, xe2x80x9clinerxe2x80x9d, xe2x80x9ccarrier sheetxe2x80x9d and xe2x80x9cbackxe2x80x9d mean the side or toward the side of the photographic label or photographic packaging material opposite from the side bearing the photosensitive imaging layers or developed image. For this invention, xe2x80x9ctransparentxe2x80x9d polymer material is defined as a polymer material that has a spectral transmission greater than 90%. For a imaging element, spectral transmission is the ratio of the transmitted power to the incident power and is expressed as a percentage as follows; TRGB=10xe2x88x92D*100 where D is the average of the red, green, and blue Status A transmission density response measured by an X-Rite model 310 (or comparable) photographic transmission densitometer.
In order to produce a pressure sensitive clear photographic label, the carrier sheet material that carries the pressure sensitive adhesive, pragmatic sheet and silver halide imaged layers, the carrier sheet material must allow for efficient transport in manufacturing, image printing, image development, label converting and label application equipment. Further, since the silver halide image is clear and does not contain white pigment to reflect printing light energy toward the emulsion layers for a secondary exposure, a means of reducing the secondary exposure is critical to image and text quality of the photographic label. An imaging element comprising at least one imaging layer wherein said imaging layer comprises photosensitive silver halide layer comprising dye forming couplers, a transparent polymer pragmatic sheet below said at least one imaging layer, an adhesive layer below said pragmatic sheet, and a black carrier sheet below said adhesive layer is preferred. The photographic label of the invention is preferred as the black, stiff carrier sheet allows for efficient transport through photographic printing and processing equipment and absorbs printing light energy so that unwanted secondary exposure of the silver halide imaging layers are avoided. Unwanted secondary exposure of the silver halide imaging layers results in a loss in image sharpness and text quality.
A black carrier sheet is preferred as a black carrier sheet has been shown to absorb the printing light energy and not reflect the light energy back toward the light sensitive imaging layers. A carrier sheet with an L* of less than has been shown to sufficiently reduce the problems with a unwanted secondary exposure of the light sensitive silver halide imaging layers. Any pigment or dyes well known in the art can be used to create the black carrier sheet. Examples of these include carbon black and dark dye sets such as perylene violet, phthalocyanine blue and carbazole violet.
A carrier with a roughness average of less than 0.20 micrometers is preferred as the pragmatic sheet tends to conform to the roughness of the carrier sheet. A rough carrier sheet, a carrier sheet with a roughness average greater than 0.30 micrometers has been shown to impart unwanted roughness to the pragmatic sheet resulting in entrained air during the labeling operation. Entrained air during labeling significantly reduces the quality of the label as entrained air, causes optical distortion. The most preferred roughness average of the carrier sheet is between 0.10 and 0.18 micrometer. Above 0.25 micrometers, entrained air during labeling becomes evident. Below 0.08 micrometers, little improvement in labeling is observed and therefore is not cost justified.
Another preferred method for managing the secondary exposure of the light sensitive silver halide imaging layers is to provide a highly reflective white carrier sheet. A carrier sheet with an L* greater than 92 has been shown to produce silver halide images that are high in quality, sharp and have excellent text quality compared to prior art carrier materials that have an L* less than 88. The preferred method for producing a carrier sheet with an L* greater than 92 is by the addition of white pigment such as TiO2 or barium sulfate into the carrier sheet. White pigment addition of 12% by weight has been shown to produce a high quality transparent silver halide label.
A further advantage of using a highly reflective white carrier sheet is higher photographic sensitivity of the silver halide imaging system. Higher sensitivity is achieved by exposure by both incident light from the printing source, and reflected light off of the highly reflective white carrier sheet. This is in contrast to using a black carrier sheet, in which only incident light exposes the light sensitive silver halide emulsions. The back reflection approximately doubles the photographic sensitivity of the system. This can result in higher printing productivity.
Another advantage of using a highly reflective white carrier sheet is in densitometry of the media. A media comprising a black carrier sheet would not be suitable to densitometer as the black carrier sheet would absorb all incident light before a reflected light reading could be made. Therefore, the pragmatic sheet would need to be stripped from the carrier layer and applied to a white reflective surface prior to densitometry. This extra step could be avoided if the media was designed with a highly reflective white carrier sheet.
A peelable carrier sheet or back is preferred as the pressure sensitive adhesive required for adhesion of the label to the package can not be transported through labeling equipment without the carrier sheet. The carrier sheet provides strength for conveyance and protects the pressure sensitive adhesive prior to application to the package. A preferred carrier sheet material is cellulose paper. A cellulose paper carrier sheet is flexible, strong and low in cost compared to polymer substrates. Further, a cellulose paper substrate allows for a textured label surface that can be desirable in some packaging applications. The paper may be provided with coatings that will provide waterproofing to the paper as the photographic element of the invention must be processed in aqueous chemistry to develop the image. Examples of suitable water proof coatings applied to the paper are acrylic polymer, melt extruded polyethylene and oriented polyolefin sheets laminated to the paper. Paper is also preferred as paper can contain moisture and salt which provide antistatic properties that prevent static sensitization of the silver halide image layers.
Further, paper containing sizing agents, known in the photographic paper art and disclosed in U.S. Pat. No. 6,093,521, provide resistance to edge penetration of the silver halide image processing chemistry. An edge penetration of less than 8 mm is preferred as processing chemistry penetrated into the paper greater than 12 mm has been shown to swell causing die cutting problems when pragmatic sheet matrix is die cut and stripped from the carrier sheet. Also, penetration of processing chemistry greater than 12 mm increases the chemistry usage in processing resulting in a higher processing costs.
Another preferred carrier sheet material or peelable back is an oriented sheet of polymer. The carrier sheet preferably is an oriented polymer because of the strength and toughness developed in the orientation process. Preferred polymers for the carrier sheet substrate include polyolefins, polyester and nylon. Preferred polyolefin polymers include polypropylene, polyethylene, polymethylpentene, polystyrene, polybutylene, and mixtures thereof. Polyolefin copolymers, including copolymers of propylene and ethylene such as hexene, butene, and octene are also useful. Polyester is most preferred, as it is has desirable strength and toughness properties required for efficient transport of silver halide pressure sensitive label carrier sheet in high speed labeling equipment.
In another preferred embodiment, the carrier sheet consists of a paper core to which sheets of oriented polymer are laminated. The laminated paper carrier sheet is preferred because the oriented sheets of polymer provide tensile strength which allows the thickness of the carrier sheet to be reduced compared to coated paper and the oriented polymer sheet provides resistance to curl during manufacturing and drying in the silver halide process.
The tensile strength of the carrier sheet or the tensile stress at which a substrate breaks apart is an important conveyance and forming parameter. Tensile strength is measured by ASTM D882 procedure. A tensile strength greater than 120 MPa is preferred as carrier sheets less than 110 MPa begin to fracture in automated packaging equipment during conveyance, forming and application to the package.
The coefficient of friction or COF of the carrier sheet containing the silver halide imaging layer is an important characteristic as the COF is related to conveyance and forming efficiency in automated labeling equipment. COF is the ratio of the weight of an item moving on a surface to the force that maintains contact between the surface and the item. The mathematical expression for COF is as follows:
COF=xcexc=(friction force/normal force)
The COF of the carrier sheet is measured using ASTM D-1894 utilizing a stainless steel sled to measure both the static and dynamic COF of the carrier sheet. The preferred COF for the carrier sheet of the invention is between 0.2 and 0.6. As an example, a 0.2 COF is necessary for coating on a label used in a pick-and-place application. The operation using a mechanical device to pick a label and move it to another point requires a low COF so the label will easily slide over the surface of the label below it. At the other extreme, large sheets such as book covers require a 0.6 COF to prevent them from slipping and sliding when they are piled on top of each other in storage. Occasionally, a particular material may require a high COF on one side and a low COF on the other side. Normally, the base material itself, such as a plastic film, foil, or paper substrate, would provide the necessary COF for one side. Application of an appropriate coating would modify the image side to give the higher or lower value. Conceivably, two different coatings could be used with one on either side. COF can be static or kinetic. The coefficient of static friction is the value at the time movement between the two surfaces is ready to start but no actual movement has occurred. The coefficient of kinetic friction refers to the case when the two surfaces are actually sliding against each other at a constant rate of speed. COF is usually measured by using a sled placed on the surface. The force necessary at the onset of sliding provides a measurement of static COF. Pulling the sled at a constant speed over a given length provides a measure of kinetic frictional force.
The preferred thickness of the carrier sheet of the invention is between 75 and 225 micrometers. Thickness of the carrier sheet is important in that the strength of the carrier sheet, expressed in terms of tensile strength or mechanical modulus, must be balanced with the thickness of the carrier sheet to achieve a cost efficient design. For example, thick carrier sheets that are high in =strength are not cost efficient because thick carrier sheets will result in short roll lengths compared to thin carrier sheets at a given roll diameter. A carrier sheet thickness less that 60 micrometers has been shown to cause transport failure in the edge guided silver halide printers. A carrier sheet thickness greater than 250 micrometers yields a design that is not cost effective and is difficult to transport in existing silver halide printers.
The carrier sheet of the invention preferably has an optical transmission of less than 20%. During the printing of the silver halide labels, exposure light energy is required to reflect from the pragmatic sheet/carrier sheet combination to yield a secondary exposure. This secondary exposure is critical to maintaining a high level of printing productivity. It has been shown that carrier sheets with an optical transmission of greater than 25% significantly reduces the printing speed of the silver halide label. Further, clear pragmatic sheet material to provide the xe2x80x9cno label lookxe2x80x9d need an opaque carrier sheet to not only maintain printing speed, but to prevent unwanted reflection from printing platens in current silver halide printers.
Since the light sensitive silver halide layers of the invention can suffer from unwanted exposure from static discharge during manufacturing, printing and processing, the line preferably has a resistivity of less than 1011 ohms/square. A wide variety of electrically-conductive materials can be incorporated into antistatic layers to produce a wide range of conductivities. These can be divided into two broad groups: (i) ionic conductors and (ii) electronic conductors. In ionic conductors charge is transferred by the bulk diffusion of charged species through an electrolyte. Here the resistivity of the antistatic layer is dependent on temperature and humidity. Antistatic layers containing simple inorganic salts, alkali metal salts of surfactants, ionic conductive polymers, polymeric electrolytes containing alkali metal salts, and colloidal metal oxide sols (stabilized by metal salts), described previously in patent literature, fall in this category. However, many of the inorganic salts, polymeric electrolytes, and low molecular weight surfactants used are water-soluble and are leached out of the antistatic layers during processing, resulting in a loss of antistatic function. The conductivity of antistatic layers employing an electronic conductor depends on electronic mobility rather than ionic mobility and is independent of humidity. Antistatic layers which contain conjugated polymers, semiconductive metal halide salts, semiconductive metal oxide particles, etc. have been described previously. However, these antistatic layers typically contain a high volume percentage of electronically conducting materials which are often expensive and impart unfavorable physical characteristics, such as color, increased brittleness, and poor adhesion to the antistatic layer.
In a preferred embodiment of this invention the label has an antistat material incorporated into the carrier sheet or coated on the carrier sheet. It is desirable to have an antistat that has an electrical surface resistivity of at least 1011 log ohms/square. In the most preferred embodiment, the antistat material comprises at least one material selected from the group consisting of tin oxide and vanadium pentoxide.
In another preferred embodiment of the invention antistatic material are incorporated into the pressure sensitive adhesive layers. The antistatic material incorporated into the pressure sensitive adhesive layer provides static protection to the silver halide layers and reduces the static on the label which has been shown to aid labeling of containers in high speed labeling equipment. As a stand-alone or supplement to the carrier sheet comprising an antistatic layer, the pressure sensitive adhesive may also further comprise an antistatic agent selected from the group consisting of conductive metal oxides, carbon particles, and synthetic smectite clay, or multilayered with an inherently conductive polymer. In one of the preferred embodiments, the antistat material is metal oxides. Metal oxides are preferred because they are readily dispersed in the thermoplastic adhesive and can be applied to the polymer sheet by any means known in the art. Conductive metal oxides that may be useful in this invention are selected from the group consisting of conductive particles including doped-metal oxides, metal oxides containing oxygen deficiencies, metal antimonates, conductive nitrides, carbides, or borides, for example, TiO2, SnO2, Al2O3, ZrO3, In2O3, MgO, ZnSb2O6, InSbO4, TiB2, ZrB2, NbB2, TaB2, CrB2, MoB, WB, LaB6, ZrN, TiN, TiC, and WC. The most preferred materials are tin oxide and vanadium pentoxide because they provide excellent conductivity and are transparent.
In order to provide a digital printing technology that can be applied to a package that is high in quality, can handle text, graphic and images, is economical for short run printing jobs and accurately reproduce flesh tones, silver halide imaging is preferred. The silver halide technology can be either black and white or color. The silver halide imaging layers are preferably exposed and developed prior to application to a package. The clear pragmatic sheet of the invention contains the necessary tensile strength properties and coefficient of friction properties to allow for efficient transport and application of the images in high speed labeling equipment. The clear pragmatic sheet of the invention is formed by applying light sensitive silver halide imaging layers of a transparent flexible label stock or pragmatic sheet that contains a pressure sensitive adhesive. The imaging layers, pragmatic sheet and pressure sensitive adhesive are supported and transported through labeling equipment using a tough carrier sheet material. Because the light sensitive silver halide imaging layers are vulnerable to environmental solvents such as water, coffee and hand oils, an environmental protection layer is preferably applied to the light sensitive silver halide imaging layers after image development.
The environmental protection layer may consist of suitable material that protects the image from environmental solvents, resists scratching, and does not interfere with the image quality. The environmental protection layer is preferably applied to the photographic image after image development because the liquid processing chemistry required for image development must be able to efficiently penetrate the surface of the imaging layers to contact the silver halide and couplers utilizing typical silver halide imaging processes. The environmental protection layer would be generally impervious to developer chemistry. An environmental protection layer where transparent polymer particles are applied to the topmost surface of the imaging layers in the presence of an electric field and fused to the topmost layer causing the transparent polymer particles to form a continuous polymeric layer is preferred. An electrophotographic toner applied polymer is preferred, as it is an effective way to provide a thin, protective environmental layer to the photographic label that has been shown to withstand environmental solvents and damage due to handling.
In another embodiment, the environmental protection layer is coatable from aqueous solution, which survives exposure and processing, and forms a continuous, water-impermeable protective layer in a post-process fusing step. The environmental protection layer is preferably formed by coating polymer beads or particles of 0.1 to 50 xcexcm in average size together with a polymer latex binder on the emulsion side of a sensitized photographic product. Optionally, a small amount of water-soluble coating aids (viscosifiers, surfactants) can be included in the layer, as long as they leach out of the coating during processing. After exposure and processing, the product with image is treated in such a way as to cause fusing and coalescence of the coated polymer beads, by heat and/or pressure (fusing), solvent treatment, or other means so as to form the desired continuous, water impermeable protective layer.
Examples of suitable polymers from which the polymer particles used in environmental protection layer can be selected include poly(vinyl chloride), poly(vinylidene chloride), poly(vinyl chloride-co-vinylidene chloride), chlorinated polypropylene, poly(vinyl chloride-co-vinyl acetate), poly(vinyl chloride-co-vinyl acetate-co-maleic anhydride), ethyl cellulose, nitrocellulose, poly(acrylic acid) esters, linseed oil-modified alkyd resins, rosin-modified alkyd resins, phenol-modified alkyd resins, phenolic resins, polyesters, poly(vinyl butyral), polyisocyanate resins, polyurethanes, poly(vinyl acetate), polyamides, chroman resins, dammar gum, ketone resins, maleic acid resins, vinyl polymers, such as polystyrene and polyvinyltoluene or copolymer of vinyl polymers with methacrylates or acrylates, poly(tetrafluoroethylene-hexafluoropropylene), low-molecular weight polyethylene, phenol-modified pentaerythritol esters, poly(styrene-co-indene-co-acrylonitrile), poly(styrene-co-indene), poly(styrene-co-acrylonitrile), poly(styrene-co-butadiene), poly(stearyl methacrylate) blended with poly(methyl methacrylate), copolymers with siloxanes and polyalkenes. These polymers can be used either alone or in combination. In a preferred embodiment of the invention, the polymer comprises a polyester or poly(styrene-co-butyl acrylate). Preferred polyesters are based on ethoxylated and/or propoxylated bisphenol A and one or more of terephthalic acid, dodecenylsuccinic acid and fumaric acid as they form an acceptable environmental protection layer that generally survives the rigors of a packaging label.
To increase the abrasion resistance of the environmental protection layer, polymers which are cross-linked or branched can be used. For example, poly(styrene-co-indene-co-divinylbenzene), poly(styrene-co-acrylonitrile-co-divinylbenzene), or poly(styrene-co-butadiene-co-divinylbenzene) can be used.
The polymer particles for the environmental protection layer should be transparent, and are preferably colorless. But it is specifically contemplated that the polymer particle can have some color for the purposes of color correction, or for special effects, so long as the image is viewable through the overcoat. Thus, there can be incorporated into the polymer particle dye which will impart color. In addition, additives can be incorporated into the polymer particle which will give to the overcoat desired properties. For example, a UV absorber can be incorporated into the polymer particle to make the overcoat UV absorptive, thus protecting the image from UV induced fading or blue tint can be incorporated into the polymer particle to offset the native yellowness of the gelatin used in the silver halide imaging layers.
In addition to the polymer particles which form the environmental protection layer, there can be combined with the polymer composition other particles which will modify the surface characteristics of the element. Such particle are solid and nonfusible at the conditions under which the polymer particles are fused, and include inorganic particles, like silica, and organic particles, like methylmethacrylate beads, which will not melt during the fusing step and which will impart surface roughness to the overcoat.
The surface characteristics of the environmental protection layer are in large part dependent upon the physical characteristics of the polymer which forms the toner and the presence or absence of solid, nonfusible particles. However, the surface characteristics of the overcoat also can be modified by the conditions under which the surface is fused. For example, the surface characteristics of the fusing member that is used to fuse the toner to form the continuous overcoat layer can be selected to impart a desired degree of smoothness, texture or pattern to the surface of the element. Thus, a highly smooth fusing member will give a glossy surface to the imaged element, a textured fusing member will give a matte or otherwise textured surface to the element, a patterned fusing member will apply a pattern to the surface of the element.
Suitable examples of the polymer latex binder include a latex copolymer of butyl acrylate, 2-acrylamido-2-methylpropanesulfonate, and acetoacetoxyethylmethacrylate. Other latex polymers which are useful include polymers having a 20 to 10,000 nm diameter and a Tg of less than 60xc2x0 C. suspended in water as a colloidal suspension.
Examples of suitable coating aids for the environmental protection layer include any water soluble polymer or other material that imparts appreciable viscosity to the coating suspension, such as high MW polysaccharide derivatives (e.g. xanthan gum, guar gum, gum acacia, Keltrol (an anionic polysaccharide supplied by Merck and Co., Inc.) high MW polyvinyl alcohol, carboxymethylcellulose, hydroxyethylcellulose, polyacrylic acid and its salts, polyacrylamide, etc). Surfactants include any surface active material that will lower the surface tension of the coating preparation sufficiently to prevent edge-withdrawal, repellencies, and other coating defects. These include alkyloxy- or alkylphenoxypolyether or polyglycidol derivatives and their sulfates, such as nonylphenoxypoly(glycidol) available from Olin Matheson Corporation or sodium octylphenoxypoly(ethyleneoxide) sulfate, organic sulfates or sulfonates, such as sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium bis(2-ethylhexyl)sulfosuccinate (Aerosol OT), and alkylcarboxylate salts such as sodium decanoate.
The application of an ultraviolet polymerizable monomers and oligomers to the outermost layer of the developed silver halide imaging layers and subsequent radiation exposure to form a thin cross-linked protective layer is preferred. UV cure polymers are preferred, as they can easily be applied to the outermost layer of the silver halide imaging layers and have been shown to provide an acceptable protective layer for the silver halide label material. Preferred UV cure polymers include aliphatic urethane, allyl methacrylate, ethylene glycol dimethacrylate, polyisocyanate and hydroxyethyl methacrylate. A preferred photoinitiator is benzil dimethyl ketal. The preferred intensity of radiation is between 0.1 and 1.5 milliwatt/cm2. Below 0.05, insufficient cross-linking occurs yielding a protective layer that does not offer sufficient protection for the labeling of packages.
The application of a pre-formed polymer layer to the outermost surface of the developed label silver halide image to form an environmental protection layer is most preferred. Application of a pre-formed sheet is preferred because pre-formed sheets are tough and durable easily withstanding the environmental solvents and handling forces applied to the silver halide imaged label. Application of the pre-formed polymer sheet is preferable carried out though lamination after image development. An adhesive is applied to either the photographic label or the pre-formed polymer sheet prior to a pressure nip that adheres the two surfaces and eliminates any trapped air that would degrade the quality of the image.
The pre-formed sheet preferably is an oriented polymer because of the strength and toughness developed in the orientation process. Preferred polymers for the flexible substrate include polyolefins, polyester and nylon. Preferred polyolefins include polypropylene, polyethylene, polymethylpentene, polystyrene, polybutylene, and mixtures thereof Polyolefin copolymers, including copolymers of propylene and ethylene such as hexene, butene, and octene are also useful. Polypropylene is most preferred, as it is low in cost and has desirable strength and toughness properties required for a pressure sensitive label.
The application of a synthetic latex to the developed silver halide label image is another preferred environmental protection layer. A coating of synthetic latex has been shown to provide an acceptable environmental protection layer and can be coated in an aqueous solution eliminating exposure to solvents. The coating of latex has been shown to provide an acceptable environmental protection layer for the silver halide packaging label. Preferred synthetic latexes for the environmental protection layer are made by emulsion polymerization techniques from styrene butadiene copolymer, acrylate resins, and polyvinyl acetate. The preferred particles size for the synthetic latex ranges from 0.05 to 0.15 xcexcm. The synthetic latex is applied to the outermost layer of the silver halide imaging layers by known coating methods that include rod coating, roll coating and hopper coating. The synthetic latexes must be dried after application and must dry transparent so as not to interfere with the quality of the silver halide image.
The pragmatic sheet material, or the flexible substrate utilized in this invention on to which the light sensitive silver halide imaging layers are applied, must not interfere with the silver halide imaging layers. Further, the pragmatic sheet material of this invention needs to optimize the performance of the silver halide imaging system. Suitable flexible substrates must also perform efficiently in an automated packaging equipment for the application of labels to various containers. Transparent pragmatic sheet are preferred to produce a clear label. Optical transmission of the pragmatic sheet greater than 90% is preferred as optical transmission less than 88% appear cloudy and do not blend into the background of the package. Transparent polymer substrates are preferred pragmatic sheet material because they are tear resistant, have excellent conformability, good chemical resistance and high in strength. Preferred polymer substrates include polyester, oriented polyolefin such as polyethylene and polypropylene, cast polyolefins such as polypropylene and polyethylene, polystyrene, acetate and vinyl. Polymers are preferred as they are strong flexible, transparent and provide an excellent surface for the coating of silver halide imaging layers.
Biaxially oriented polyolefm sheets are preferred as they are low in cost, have excellent optical properties that optimize the silver halide system, and can be applied to packages in high speed labeling equipment. The flexible polymer pragmatic sheet substrate may contain more than one layer. The skin layers of the flexible substrate can be made of the same polymeric materials as listed above for the core matrix. The composite sheet can be made with skin(s) of the same polymeric material as the core matrix, or it can be made with skin(s) of different polymeric composition than the core matrix. For compatibility, an auxiliary layer can be used to promote adhesion of the skin layer to the core.
The total thickness of the topmost skin layer of the polymeric pragmatic sheet substrate may be between 0.20 xcexcm and 1.5 xcexcm, preferably between 0.5 and 1.0 xcexcm. Below 0.5 xcexcm any inherent nonplanarity in the coextruded skin layer may result in unacceptable color variation. At skin thickness greater than 1.0 xcexcm, there is a reduction in the photographic optical properties such as image resolution. At thickness greater than 1.0 xcexcm, there is also a greater material volume to filter for contamination such as clumps or poor color pigment dispersion.
Addenda may be added to the topmost skin layer of the flexible pragmatic sheet substrate to change the color of the imaging element. For labeling use, a white substrate with a slight bluish tinge is preferred. The addition of the slight bluish tinge may be accomplished by any process which is known in the art including the machine blending of color concentrate prior to extrusion and the melt extrusion of blue colorants that have been preblended at the desired blend ratio. Colored pigments that can resist extrusion temperatures greater than 320xc2x0 C. are preferred, as temperatures greater than 320xc2x0 C. are necessary for coextrusion of the skin layer. Blue colorants used in this invention may be any colorant that does not have an adverse impact on the imaging element. Preferred blue colorants include Phthalocyanine blue pigments, Cromophtal blue pigments, Irgazin blue pigments, and Irgalite organic blue pigments. Optical brightener may also be added to the skin layer to absorb UV energy and emit light largely in the blue region. TiO2 may also be added to the skin layer Addenda may be added to the flexible pragmatic sheet substrate of this invention so that when the biaxially oriented sheet is viewed from a surface, the imaging element emits light in the visible spectrum when exposed to ultraviolet radiation. Emission of light in the visible spectrum allows for the support to have a desired background color in the presence of ultraviolet energy. This is particularly useful when images are viewed outside as sunlight contains ultraviolet energy and may be used to optimize image quality for consumer and commercial applications.
Addenda known in the art to emit visible light in the blue spectrum are preferred. Consumers generally prefer a slight blue tint to the density minimum areas of a developed image defined as a negative b* compared to a neutral density minimum defined as a b* within one b* unit of zero b* is the measure of yellow/blue in CIE (Commnission Internationale de L""Eclairage) space. A positive b* indicates yellow, while a negative b* indicates blue. The addition of addenda that emits in the blue spectrum allows for tinting the support without the addition of colorants which would decrease the whiteness of the image. The preferred emission is between 1 and 5 delta b* units. Delta b* is defined as the b* difference measured when a sample is illuminated with a ultraviolet light source and a light source without any significant ultraviolet energy. Delta b* is the preferred measure to determine the net effect of adding an optical brightener to the top biaxially oriented sheet of this invention. Emissions less than 1 b* unit cannot be noticed by most customers; therefore, is it not cost effective to add optical brightener to the biaxially oriented sheet when the b* is changed by less than 1 b* unit. An emission greater that 5 b* units would interfere with the color balance of the images making the whites appear too blue for most consumers.
The preferred addenda is an optical brightener. An optical brightener is a colorless, fluorescent, organic compound that absorbs ultraviolet light and emits it as visible blue light. Examples include, but are not limited to, derivatives of 4,4xe2x80x2-diaminostilbene-2,2xe2x80x2-disulfonic acid, coumarin derivatives such as 4-methyl-7-diethylaminocoumarin, 1-4-Bis (O-Cyanostyryl) Benzol and 2-Amino-4-Methyl Phenol. The optical brightener may be added to any layer in the multilayer coextruded flexible pragmatic sheet substrate. The preferred location is adjacent to or in the exposed surface layer of said sheet. This allows for the efficient concentration of optical brightener.
When the desired weight percentage loading of the optical brightener begins to approach a concentration at which the optical brightener migrates to the surface of the support forming crystals in the imaging layer, the addition of optical brightener into the layer adjacent to the exposed layer is preferred. In prior art imaging supports that use optical brightener, expensive grades of optical brightener are used to prevent migration into the imaging layer. When optical brightener migration is a concern, as with light sensitive silver halide imaging systems, the preferred exposed layer comprises polyethylene that is substantially free of optical brightener. In this case, the migration from the layer adjacent to the exposed layer is significantly reduced because the exposed surface layer acts as a barrier for optical brightener migration allowing for much higher optical brightener levels to be used to optimize image quality. Further, locating the optical brightener in the layer adjacent to the exposed layer allows for a less expensive optical brightener to be used as the exposed layer, which is substantially free of optical brightener, prevents significant migration of the optical brightener. Another preferred method to reduce unwanted optical brightener migration in biaxially oriented sheets of this invention is to use polypropylene for the layer adjacent to the exposed surface.
The coextrusion, quenching, orienting, and heat setting of the flexible pragmatic sheet substrate may be effected by any process which is known in the art for producing oriented sheet, such as by a flat sheet process or a bubble or tubular process. The flat sheet process involves extruding the blend through a slit die and rapidly quenching the extruded web upon a chilled casting drum so that the core matrix polymer component of the sheet and the skin components(s) are quenched below their glass solidification temperature. The quenched sheet is then biaxially oriented by stretching in mutually perpendicular directions at a temperature above the glass transition temperature and below the melting temperature of the matrix polymers. The sheet may be stretched in one direction and then in a second direction or may be simultaneously stretched in both directions. After the sheet has been stretched, it is heat set by heating to a temperature sufficient to crystallize or anneal the polymers, while restraining to some degree the sheet against retraction in both directions of stretching.
A pressure sensitive photographic label adhesive is utilized in the invention to allow the developed silver halide packaging label to be adhered to the surface of the package typically utilizing high speed packaging equipment. xe2x80x9cPeelable separationxe2x80x9d or xe2x80x9cpeel strengthxe2x80x9d or xe2x80x9cseparation forcexe2x80x9d is a measure of the amount of force required to separate the silver halide label from the package to which the label has been applied. The peel strength is the amount of force required to separate two surfaces that are held together by internal forces of the photographic label adhesive which consist of valence forces or interlocking action, or both. Peel strength is measured using an Instron gauge and peeling the sample at 180 degrees with a crosshead speed of 1.0 meters/min. The sample width is 5 cm and the distance peeled is 10 cm in length.
A substrate that comprises a release layer for a photographic label adhesive that repositions is preferred. The release layer allows for uniform separation of the photographic label adhesive at the photographic label adhesive base interface. The release layer may be applied to the carrier sheet by any method known in the art for applying a release layer to substrates. Examples include silicone coatings, tetrafluoroethylene fluorocarbon coatings, fluorinated ethylene-propylene coatings, and calcium stearate.
Preferred pressure sensitive adhesive for use with the transparent label of the invention has an optical transmission greater than 90%. Adhesives with an optical transmission less than 85% are cloudy and detract from the quality of the silver halide printed image.
Preferred transparent photographic label adhesives of this invention must not interact with the light sensitive silver halide imaging system so that image quality is deteriorated. Further, since photographic elements of this invention must be photoprocessed, the performance of the photographic label adhesive of this invention must not be deteriorated by photographic processing chemicals. Suitable photographic label adhesive may be inorganic or organic, natural or synthetic, that is capable of bonding the image to the desired surface by surface attachment. Examples of inorganic photographic label adhesives are soluble silicates, ceramic and thermosetting powdered glass. Organic photographic label adhesives may be natural or synthetic. Examples of natural organic photographic label adhesives include bone glue, soybean starch cellulosics, rubber latex, gums, terpene, mucilages and hydrocarbon resins. Examples of synthetic organic photographic label adhesives include elastomer solvents, polysulfide sealants, thermoplastic resins such as isobutylene and polyvinyl acetate, thermosetting resins such as epoxy, phenoformaldehyde, polyvinyl butyral and cyanoacrylates and silicone polymers. For single or multiple layer photographic label adhesive systems, the preferred photographic label adhesive composition is selected from the group consisting of natural rubber, synthetic rubber, acrylics, acrylic copolymers, vinyl polymers, vinyl acetate-, urethane, acrylate-type materials, copolymer mixtures of vinyl chloride-vinyl acetate, polyvinylidene, vinyl acetate-acrylic acid copolymers, styrene butadiene, carboxylated stryrene butadiene copolymers, ethylene copolymers, polyvinyl alcohol, polyesters and copolymers, cellulosic and modified cellulosic, starch and modified starch compounds, epoxies, polyisocyanate, polyimides.
For single or multiple layer photographic transparent label adhesive systems, the preferred permanent photographic label adhesive composition is selected from the group consisting of epoxy, phenoformaldehyde, polyvinyl butyral, cyanoacrylates, rubber based photographic label adhesives, styrene/butadiene based photographic label adhesives, acrylics and vinyl derivatives. Peelable photographic label adhesives and permanent photographic label adhesives may be used in combination in the same layer or in different locations in the photographic support structure.
The silver halide imaging layers on a pressure sensitive substrate preferably are applied to a variety of packages in automated labeling equipment. Preferred package types are bottles, cans, stand-up pouches, boxes, and bags. The packages may contain materials that require a package for sale. Preferred materials that are packaged include liquids and particulate materials.
The transparent silver halide packaging label of the invention preferably has a thickness of less than 600 xcexcm. A silver halide packaging label greater than 650 xcexcm in thickness offers no significant improvement in either imaging quality or packaging label performance. Further, transport through high speed packaging equipment is difficult at a photographic label thickness greater than 650 xcexcm and stripping the photographic labels utilizing the Bernoulli method is difficult if the thickness of the photographic label exceeds 700 xcexcm.
The following is an example of a preferred clear silver halide pressure sensitive label structure that has an environmental protection layer (EPL) applied to the outermost silver halide imaging layer. The polyethylene and polypropylene layers are an integral biaxially oriented sheet, to which the pressure sensitive adhesive and carrier sheet material containing an extruded black layer are laminated prior to the coating of the light sensitive silver halide imaging layers.
7.5 xcexcm ground styrene butyl acrylate fused EPL
Layer of silver halide formed image
Polyethylene with a density of 0.925 g/cc
Polypropylene
Acrylic pressure sensitive adhesive
Silicone release layer
Polyproplyene with 12% carbon black
Cellulose paper
Oriented polypropylene
The following is an example of a preferred clear silver halide pressure sensitive label structure after an environmental protection layer (EPL) is applied to the outermost developed silver halide imaging layer, and after opaque inks have been applied over the adhesive layer after temporarily or permanently removing the carrier sheet from the pragmatic sheet. The polyethylene and polypropylene layers are an integral biaxially oriented sheet, to which the pressure sensitive adhesive and liner material are laminated prior to the coating of the light sensitive silver halide imaging layers. The opaque inks are applied after image exposure and photo-processing the material, and after the liner is temporarily or permanently removed from the media.
Pragmatic Sheet
7.5 xcexcm ground styrene butyl acrylate fused EPL
Layer of silver halide formed image
Polyethylene with a density of 0.925 g/cc
Polypropylene
Acrylic pressure sensitive adhesive
Opaque inks
Carrier Sheet: Reapplied if Necessary
Silicone release layer
Polyproplyene with 12% carbon black
Cellulose paper
Oriented polypropylene
The following is an example of a preferred clear silver halide pressure sensitive pragmatic sheet structure after an environmental protection layer (EPL) is applied to the outermost developed silver halide imaging layer, and after opaque inks have been applied to the opposite side of the pragmatic sheet from the emulsion, and an adhesive layer applied over said opaque inks, followed by immediate application to a package or immediate attachment to a carrier sheet for future application. The opaque inks are applied after image exposure and photo-processing the material.
7.5 xcexcm ground styrene butyl acrylate fused EPL
Layer of silver halide formed image
Polyethylene with a density of 0.925 g/cc
Polypropylene
Opaque inks
Acrylic pressure sensitive adhesive (applied after printing inks)
Disclosed below is a suitable flesh tone optimized light sensitive silver halide emulsion capable of accurately reproducing flesh tones and label text. This invention is also directed to a silver halide packaging label capable of excellent performance when exposed by either an electronic printing method or a conventional optical printing method. An electronic printing method comprises subjecting a radiation sensitive silver halide emulsion layer of a recording element to actinic radiation of at least 10xe2x88x924 ergs/cm2 for up to 100 xcexcseconds duration in a pixel-by-pixel mode wherein the silver halide emulsion layer is comprised of silver halide grains as described above. A conventional optical printing method comprises subjecting a radiation sensitive silver halide emulsion layer of a recording element to actinic radiation of at least 10xe2x88x924 ergs/cm2 for 10xe2x88x923 to 300 seconds in an imagewise mode wherein the silver halide emulsion layer is comprised of silver halide grains as described above.
This invention in a preferred embodiment utilizes a radiation-sensitive emulsion comprised of silver halide grains (a) containing greater than 50 mole percent chloride, based on silver, (b) having greater than 50 percent of their surface area provided by {100} crystal faces, and (c) having a central portion accounting for from 95 to 99 percent of total silver and containing two dopants selected to satisfy each of the following class requirements: (i) a hexacoordination metal complex which satisfies the formula
[ML6]nxe2x80x83xe2x80x83(I)
wherein n is zero, xe2x88x921, xe2x88x922, xe2x88x923 or xe2x88x924; M is a filled frontier orbital polyvalent metal ion, other than iridium; and L6 represents bridging ligands which can be independently selected, provided that least four of the ligands are anionic ligands, and at least one of the ligands is a cyano ligand or a ligand more electronegative than a cyano ligand; and (ii) an iridium coordination complex containing a thiazole or substituted thiazole ligand.
This invention is directed towards a photographic label comprising a flexible substrate and at least one light sensitive silver halide emulsion layer comprising silver halide grains as described above. The photographic label may be color or black and white where silver is retained in the developed imaging layer to form density.
It has been discovered quite surprisingly that the combination of dopants (i) and (ii) provides greater reduction in reciprocity law failure than can be achieved with either dopant alone. Further, unexpectedly, the combination of dopants (i) and (ii) achieve reductions in reciprocity law failure beyond the simple additive sum achieved when employing either dopant class by itself. It has not been reported or suggested prior to this invention that the combination of dopants (i) and (ii) provides greater reduction in reciprocity law failure, particularly for high intensity and short duration exposures. The combination of dopants (i) and (ii) further unexpectedly achieves high intensity reciprocity with iridium at relatively low levels, and both high and low intensity reciprocity improvements even while using conventional gelatino-peptizer (e.g., other than low methionine gelatino-peptizer).
In a preferred practical application, the advantages of the invention can be transformed into increased throughput of digital substantially artifact-free color print images while exposing each pixel sequentially in synchronism with the digital data from an image processor.
In one embodiment, the present invention represents an improvement on the electronic printing method. Specifically, this invention in one embodiment is directed to an electronic printing method which comprises subjecting a radiation sensitive silver halide emulsion layer of a recording element to actinic radiation of at least 10xe2x88x924 ergs/cm2 for up to 100 xcexcseconds duration in a pixel-by-pixel mode. The present invention realizes an improvement in reciprocity failure by selection of the radiation sensitive silver halide emulsion layer. While certain embodiments of the invention are specifically directed towards electronic printing, use of the emulsions and elements of the invention is not limited to such specific embodiment, and it is specifically contemplated that the emulsions and elements of the invention are also well suited for conventional optical printing.
It has been found that significantly improved reciprocity performance can be obtained for silver halide grains (a) containing greater than 50 mole percent chloride, based on silver, and (b) having greater than 50 percent of their surface area provided by {100} crystal faces by employing a hexacoordination complex dopant of class (i) in combination with an iridium complex dopant comprising a thiazole or substituted thiazole ligand. The reciprocity improvement is obtained for silver halide grains employing conventional gelatino-peptizer, unlike the contrast improvement described for the combination of dopants set forth in U.S. Pat. Nos. 5,783,373 and 5,783,378, which requires the use of low methionine gelatino-peptizers as discussed therein, and which states it is preferable to limit the concentration of any gelatino-peptizer with a methionine level of greater than 30 micromoles per gram to a concentration of less than 1 percent of the total peptizer employed. Accordingly, in specific embodiments of the invention, it is specifically contemplated to use significant levels (i.e., greater than 1 weight percent of total peptizer) of conventional gelatin (e.g., gelatin having at least 30 micromoles of methionine per gram) as a gelatino-peptizer for the silver halide grains of the emulsions of the invention. In preferred embodiments of the invention, gelatino-peptizer is employed which comprises at least 50 weight percent of gelatin containing at least 30 micromoles of methionine per gram, as it is frequently desirable to limit the level of oxidized low methionine gelatin which may be used for cost and certain performance reasons.
In a specific, preferred form of emulsion used in the invention, it is contemplated to employ a class (i) hexacoordination complex dopant satisfying the formula:
[ML6]nxe2x80x83xe2x80x83(I)
where
n is zero, xe2x88x921, xe2x88x922, xe2x88x923 or xe2x88x924;
M is a filled frontier orbital polyvalent metal ion, other than iridium, preferably Fe+2, Ru+2, Os+2, Co+3, Rh+3, Pd+4 or Pt+4, more preferably an iron, ruthenium or osmium ion, and most preferably a ruthenium ion;
L6 represents six bridging ligands which can be independently selected, provided that least four of the ligands are anionic ligands and at least one (preferably at least 3 and optimally at least 4) of the ligands is a cyano ligand or a ligand more electronegative than a cyano ligand. Any remaining ligands can be selected from among various other bridging ligands, including aquo ligands, halide ligands (specifically, fluoride, chloride, bromide and iodide), cyanate ligands, thiocyanate ligands, selenocyanate ligands, tellurocyanate ligands, and azide ligands. Hexacoordinated transition metal complexes of class (i) which include six cyano ligands are specifically preferred.
Illustrations of specifically contemplated class (i) hexacoordination complexes for inclusion in the high chloride grains are provided by Olm et al U.S. Pat. No. 5,503,970 and Daubendiek et al U.S. Pat. Nos. 5,494,789 and 5,503,971, and Keevert et al U.S. Pat. No. 4,945,035, as well as Murakami et al Japanese Patent Application Hei-2[1990]-249588, and Research Disclosure Item 36736. Useful neutral and anionic organic ligands for class (ii) dopant hexacoordination complexes are disclosed by Olm et al U.S. Pat. No. 5,360,712 and Kuromoto et al U.S. Pat. No. 5,462,849.
Class (i) dopant is preferably introduced into the high chloride grains after at least 50 (most preferably 75 and optimally 80) percent of the silver has been precipitated, but before precipitation of the central portion of the grains has been completed. Preferably class (i) dopant is introduced before 98 (most preferably 95 and optimally 90) percent of the silver has been precipitated. Stated in terms of the fully precipitated grain structure, class (i) dopant is preferably present in an interior shell region that surrounds at least 50 (most preferably 75 and optimally 80) percent of the silver and, with the more centrally located silver, accounts the entire central portion (99 percent of the silver), most preferably accounts for 95 percent, and optimally accounts for 90 percent of the silver halide forming the high chloride grains. The class (i) dopant can be distributed throughout the interior shell region delimited above or can be added as one or more bands within the interior shell region.
Class (i) dopant can be employed in any conventional useful concentration. A preferred concentration range is from 10xe2x88x928 to 10xe2x88x923 mole per silver mole, most preferably from 10xe2x88x926 to 5xc3x9710xe2x88x924 mole per silver mole.
The following are specific illustrations of class (i) dopants:
(i-1) [Fe(CN)6]xe2x88x924
(i-2) [Ru(CN)6]xe2x88x924
(i-3) [Os(CN)6]xe2x88x924
(i-4) [Rh(CN)6]xe2x88x923
(i-5) [Co(CN)6]xe2x88x923
(i-6) [Fe(pyrazine)(CN)5]xe2x88x924
(i-7) [RuCl(CN)5]xe2x88x924
(i-8) [OsBr(CN)5]xe2x88x924
(i-9) [RhF(CN)5]xe2x88x923
(i-10) [In(NCS)6]xe2x88x923
(i-11) [FeCO(CN)5]xe2x88x923
(i-12) [RuF2(CN)4]xe2x88x924
(i-13) [OsCl2(CN)4]xe2x88x924
(i-14) [RhI2(CN)4]xe2x88x923
(i-15) [Ga(NCS)6]xe2x88x923
(i-16) [Ru(CN)5(OCN)]xe2x88x924
(i-17) [Ru(CN)5(N3)]xe2x88x924
(i-18) [Os(CN)5(SCN)]xe2x88x924
(i-19) [Rh(CN)5(SeCN)]xe2x88x923
(i-20) [Os(CN)Cl1]xe2x88x924
(i-21) [Fe(CN)3Cl3]xe2x88x923
(i-22) [Ru(CO)2(CN)4]xe2x88x921
When the class (i) dopants have a net negative charge, it is appreciated that they are associated with a counter ion when added to the reaction vessel during precipitation. The counter ion is of little importance, since it is ionically dissociated from the dopant in solution and is not incorporated within the grain. Common counter ions known to be fully compatible with silver chloride precipitation, such as ammonium and alkali metal ions, are contemplated. It is noted that the same comments apply to class (ii) dopants, otherwise described below.
The class (ii) dopant is an iridium coordination complex containing at least one thiazole or substituted thiazole ligand. Careful scientific investigations have revealed Group VIII hexahalo coordination complexes to create deep electron traps, as illustrated R. S. Eachus, R. E. Graves and M. T. Olm J. Chem. Phys., Vol. 69, pp. 4580-7 (1978) and Physica Status Solidi A, Vol. 57, 429-37 (1980) and R. S. Eachus and M. T. Olm Annu. Rep. Prog. Chem. Sect. C. Phys. Chem., Vol. 83, 3, pp. 3-48 (1986). The class (ii) dopants employed in the practice of this invention are believed to create such deep electron traps. The thiazole ligands may be substituted with any photographically acceptable substituent which does not prevent incorporation of the dopant into the silver halide grain. Exemplary substituents include lower alkyl (e.g., alkyl groups containing 1-4 carbon atoms), and specifically methyl. A specific example of a substituted thiazole ligand which may be used in accordance with the invention is 5-methylthiazole. The class (ii) dopant preferably is an iridium coordination complex having ligands each of which are more electropositive than a cyano ligand. In a specifically preferred form the remaining non-thiazole or non-substituted-thiazole ligands of the coordination complexes forming class (ii) dopants are halide ligands.
It is specifically contemplated to select class (ii) dopants from among the coordination complexes containing organic ligands disclosed by Olm et al U.S. Pat. No. 5,360,712; Olm et al U.S. Pat. No. 5,457,021; and Kuromoto et al U.S. Pat. No. 5,462,849.
In a preferred form it is contemplated to employ as a class (ii) dopant a hexacoordination complex satisfying the formula:
[IrL16]nxe2x80x2xe2x80x83xe2x80x83(II)
wherein
nxe2x80x2 is zero, xe2x88x921, xe2x88x922, xe2x88x923 or xe2x88x924; and
L16 represents six bridging ligands which can be independently selected, provided that at least four of the ligands are anionic ligands, each of the ligands is more electropositive than a cyano ligand, and at least one of the ligands comprises a thiazole or substituted thiazole ligand. In a specifically preferred form at least four of the ligands are halide ligands, such as chloride or bromide ligands.
Class (ii) dopant is preferably introduced into the high chloride grains after at least 50 (most preferably 85 and optimally 90) percent of the silver has been precipitated, but before precipitation of the central portion of the grains has been completed. Preferably class (ii) dopant is introduced before 99 (most preferably 97 and optimally 95) percent of the silver has been precipitated. Stated in terms of the filly precipitated grain structure, class (ii) dopant is preferably present in an interior shell region that surrounds at least 50 (most preferably 85 and optimally 90) percent of the silver and, with the more centrally located silver, accounts the entire central portion (99 percent of the silver), most preferably accounts for 97 percent, and optimally accounts for 95 percent of the silver halide forming the high chloride grains. The class (ii) dopant can be distributed throughout the interior shell region delimited above or can be added as one or more bands within the interior shell region.
Class (ii) dopant can be employed in any conventional useful concentration. A preferred concentration range is from 10xe2x88x929 to 10xe2x88x924 mole per silver mole. Iridium is most preferably employed in a concentration range of from 10xe2x88x928 to 10xe2x88x925 mole per silver mole.
Specific illustrations of class (ii) dopants are the following:
(ii-1) [IrCl5(thiazole)]-2
(ii-2) [IrCl4(thiazole)2]-1
(ii-3) [IrBr5(thiazole)]-2
(ii-4) [IrBr4(thiazole)2]-1
(ii-5) [IrCl5(5-methylthiazole)]-2
(ii-6) [IrCl4(5-methylthiazole)2]-1
(ii-7) [IrBr5(5-methylthiazole)]-2
(ii-8) [IrBr4(5-methylthiazole)2]-1
In one preferred aspect of the invention in a layer using a magenta dye forming coupler, a class (ii) dopant in combination with an OsCl5(NO) dopant has been found to produce a preferred result.
Emulsions demonstrating the advantages of the invention can be realized by modifying the precipitation of conventional high chloride silver halide grains having predominantly ( greater than 50%) {100} crystal faces by employing a combination of class (i) and (ii) dopants as described above.
The silver halide grains precipitated contain greater than 50 mole percent chloride, based on silver. Preferably the grains contain at least 70 mole percent chloride and, optimally at least 90 mole percent chloride, based on silver. Iodide can be present in the grains up to its solubility limit, which is in silver iodochloride grains, under typical conditions of precipitation, about 11 mole percent, based on silver. It is preferred for most photographic applications to limit iodide to less than 5 mole percent iodide, most preferably less than 2 mole percent iodide, based on silver.
Silver bromide and silver chloride are miscible in all proportions. Hence, any portion, up to 50 mole percent, of the total halide not accounted for chloride and iodide, can be bromide. For color reflection print (i.e., color paper) uses, bromide is typically limited to less than 10 mole percent based on silver and iodide is limited to less than 1 mole percent based on silver.
In a widely used form high chloride grains are precipitated to form cubic grainsxe2x80x94that is, grains having {100} major faces and edges of equal length. In practice ripening effects usually round the edges and corners of the grains to some extent. However, except under extreme ripening conditions substantially more than 50 percent of total grain surface area is accounted for by {100} crystal faces.
High chloride tetradecahedral grains are a common variant of cubic grains. These grains contain 6 {100} crystal faces and 8 {111 } crystal faces. Tetradecahedral grains are within the contemplation of this invention to the extent that greater than 50 percent of total surface area is accounted for by {100} crystal faces.
Although it is common practice to avoid or minimize the incorporation of iodide into high chloride grains employed in color paper, it is has been recently observed that silver iodochloride grains with {100} crystal faces and, in some instances, one or more {111 } faces offer exceptional levels of photographic speed. In the these emulsions iodide is incorporated in overall concentrations of from 0.05 to 3.0 mole percent, based on silver, with the grains having a surface shell of greater than 50 xc3x85 that is substantially free of iodide and a interior shell having a maximum iodide concentration that surrounds a core accounting for at least 50 percent of total silver. Such grain structures are illustrated by Chen et al EPO 0 718 679.
In another improved form the high chloride grains can take the form of tabular grains having {100} major faces. Preferred high chloride {100} tabular grain emulsions are those in which the tabular grains account for at least 70 (most preferably at least 90) percent of total grain projected area. Preferred high chloride {100} tabular grain emulsions have average aspect ratios of at least 5 (most preferably at least  greater than 8). Tabular grains typically have thicknesses of less than 0.3 xcexcm, preferably less than 0.2 xcexcm, and optimally less than 0.07 xcexcm. High chloride {100} tabular grain emulsions and their preparation are disclosed by Maskasky U.S. Pat. Nos. 5,264,337 and 5,292,632; House et al U.S. Pat. No. 5,320,938; Brust et al U.S. Pat. No. 5,314,798; and Chang et al U.S. Pat. No. 5,413,904.
Once high chloride grains having predominantly {100} crystal faces have been precipitated with a combination of class (i) and class (ii) dopants described above, chemical and spectral sensitization, followed by the addition of conventional addenda to adapt the emulsion for the imaging application of choice can take any convenient conventional form. These conventional features are illustrated by Research Disclosure, Item 38957, cited above, particularly:
III. Emulsion washing;
IV. Chemical sensitization;
V. Spectral sensitization and desensitization;
VII. Antifoggants and stabilizers;
VIII. Absorbing and scattering materials;
IX. Coating and physical property modifying addenda; and
X. Dye image formers and modifiers.
Some additional silver halide, typically less than 1 percent, based on total silver, can be introduced to facilitate chemical sensitization. It is also recognized that silver halide can be epitaxially deposited at selected sites on a host grain to increase its sensitivity. For example, high chloride {100} tabular grains with corner epitaxy are illustrated by Maskasky U.S. Pat. No. 5,275,930. For the purpose of providing a clear demarcation, the term xe2x80x9csilver halide grainxe2x80x9d is herein employed to include the silver necessary to form the grain up to the point that the final {100} crystal faces of the grain are formed. Silver halide later deposited that does not overlie the {100} crystal faces previously formed accounting for at least 50 percent of the grain surface area is excluded in determining total silver forming the silver halide grains. Thus, the silver forming selected site epitaxy is not part of the silver halide grains while silver halide that deposits and provides the final {100} crystal faces of the grains is included in the total silver forming the grains, even when it differs significantly in composition from the previously precipitated silver halide.
Image dye-forming couplers may be included in the element such as couplers that form cyan dyes upon reaction with oxidized color developing agents which are described in such representative patents and publications as: U.S. Pat. Nos. 2,367,531; 2,423,730; 2,474,293; 2,772,162; 2,895,826; 3,002,836; 3,034,892; 3,041,236; 4,883,746 and xe2x80x9cFarbkupplerxe2x80x94Eine Literature Ubersicht,xe2x80x9d published in Agfa Mitteilungen, Band III, pp. 156-175 (1961). Preferably such couplers are phenols and naphthols that form cyan dyes on reaction with oxidized color developing agent. Also preferable are the cyan couplers described in, for instance, European Patent Application Nos. 491,197; 544,322; 556,700; 556,777; 565,096; 570,006; and 574,948.
Typical cyan couplers are represented by the following formulas:
wherein R1, R5, and R8 each represents a hydrogen or a substituent; R2 represents a substituent; R3, R4, and R7 each represents an electron attractive group having a Harnmett""s substituent constant "sgr"para of 0.2 or more and the sum of the "sgr"para values of R3 and R4 is 0.65 or more; R6 represents an electron attractive group having a Hammett""s substituent constant "sgr"para of 0.35 or more; X represents a hydrogen or a coupling-off group; Z1 represents nonmetallic atoms necessary for forming a nitrogen-containing, six-membered, heterocyclic ring which has at least one dissociative group; Z2 represents xe2x80x94C(R7)xe2x95x90 and xe2x80x94Nxe2x95x90; and Z3 and Z4 each represents xe2x80x94C(R8)xe2x95x90 and xe2x80x94Nxe2x95x90.
For purposes of this invention, an xe2x80x9cNB couplerxe2x80x9d is a dye-forming coupler which is capable of coupling with the developer 4-amino-3-methyl-N-ethyl-N-(2-methanesulfonamidoethyl) aniline sesquisulfate hydrate to form a dye for which the left bandwidth (LBW) of its absorption spectra upon xe2x80x9cspin coatingxe2x80x9d of a 3% w/v solution of the dye in di-n-butyl sebacate solvent is at least 5 nm less than the LBW for a 3% w/v solution of the same dye in acetonitrile. The LBW of the spectral curve for a dye is the distance between the left side of the spectral curve and the wavelength of maximum absorption measured at a density of half the maximum.
The xe2x80x9cspin coatingxe2x80x9d sample is prepared by first preparing a solution of the dye in di-n-butyl sebacate solvent (3% w/v). If the dye is insoluble, dissolution is achieved by the addition of some methylene chloride. The solution is filtered and 0.1-0.2 ml is applied to a clear polyethylene terephthalate support (approximately 4 cmxc3x974 cm) and spun at 4,000 RPM using the Spin Coating equipment, Model No. EC101, available from Headway Research Inc., Garland, Tex. The transmission spectra of the so prepared dye samples are then recorded.
Preferred xe2x80x9cNB couplersxe2x80x9d form a dye which, in n-butyl sebacate, has a LBW of the absorption spectra upon xe2x80x9cspin coatingxe2x80x9d which is at least 15 nm, preferably at least 25 nm, less than that of the same dye in a 3% solution (w/v) in acetonitrile.
In a preferred embodiment the cyan dye-forming xe2x80x9cNB couplerxe2x80x9d useful in the invention has the formula (IA)
wherein
Rxe2x80x2 and Rxe2x80x3 are substituents selected such that the coupler is a xe2x80x9cNB couplerxe2x80x9d, as herein defined; and
Z is a hydrogen atom or a group which can be split off by the reaction of the coupler with an oxidized color developing agent.
The coupler of formula (IA) is a 2,5-diarnido phenolic cyan coupler wherein the substituents Rxe2x80x2 and Rxe2x80x3 are preferably independently selected from unsubstituted or substituted alkyl, aryl, amino, alkoxy and heterocyclyl groups.
In a further preferred embodiment, the xe2x80x9cNB couplerxe2x80x9d has the formula (I):
wherein
Rxe2x80x3 and Rxe2x80x2xe2x80x3 are independently selected from unsubstituted or substituted alkyl, aryl, amino, alkoxy and heterocyclyl groups and Z is as hereinbefore defined;
R1 and R2 are independently hydrogen or anunsubstituted or substituted alkyl group; and
Typically, Rxe2x80x3 is an alkyl, amino or aryl group, suitably a phenyl group. Rxe2x80x2xe2x80x3 is desirably an alkyl or aryl group or a 5- to 10-membered heterocyclic ring which contains one or more heteroatoms selected from nitrogen, oxygen and sulfur, which ring group is unsubstituted or substituted.
In the preferred embodiment the coupler of formula (I) is a 2,5-diamido phenol in which the 5-amido moiety is an amide of a carboxylic acid which is substituted in the alpha position by a particular sulfone (xe2x80x94SO2xe2x88x92) group, such as, for example, described in U.S. Pat. No. 5,686,235. The sulfone moiety is an unsubstituted or substituted alkylsulfone or a heterocyclyl sulfone or it is an arylsulfone, which is preferably substituted, in particular in the meta and/or para position.
Couplers having these structures of formulae (I) or (IA) comprise cyan dye-forming xe2x80x9cNB couplersxe2x80x9d which form image dyes having very sharp-cutting dye hues on the short wavelength side of the absorption curves with absorption maxima (xcexmax) which are shifted hypsochromically and are generally in the range of 620-645 nm, which is ideally suited for producing excellent color reproduction and high color saturation in color photographic packaging labels.
Referring to formula (I), R1 and R2 are independently hydrogen or an unsubstituted or substituted alkyl group, preferably having from 1 to 24 carbon atoms and in particular 1 to 10 carbon atoms, suitably a methyl, ethyl, n-propyl, isopropyl, butyl or decyl group or an alkyl group substituted with one or more fluoro, chloro or bromo atoms, such as a trifluoromethyl group. Suitably, at least one of R1 and R2 is a hydrogen atom and if only one of R1 and R2 is a hydrogen atom then the other is preferably an alkyl group having 1 to 4 carbon atoms, more preferably one to three carbon atoms and desirably two carbon atoms.
As used herein and throughout the specification unless where specifically stated otherwise, the term xe2x80x9calkylxe2x80x9d refers to an unsaturated or saturated straight or branched chain alkyl group, including alkenyl, and includes aralkyl and cyclic alkyl groups, including cycloalkenyl, having 3-8 carbon atoms and the term xe2x80x98arylxe2x80x99 includes specifically fused aryl.
In formula (I), Rxe2x80x3 is suitably an unsubstituted or substituted amino, alkyl or aryl group or a 5- to 10-membered heterocyclic ring which contains one or more heteroatoms selected from nitrogen, oxygen and sulfur, which ring is unsubstituted or substituted, but is more suitably an unsubstituted or substituted phenyl group.
Examples of suitable substituent groups for this aryl or heterocyclic ring include cyano, chloro, fluoro, bromo, iodo, alkyl- or aryl-carbonyl alkyl- or aryl-oxycarbonyl, carbonamido, alkyl- or aryl-carbonamido, alkyl- or aryl-sulfonyl, alkyl- or aryl-sulfonyloxy, alkyl- or aryl-oxysulfonyl, alkyl- or aryl-sulfoxide, alkyl- or aryl-sulfamoyl, alkyl- or aryl-sulfonamido, aryl, alkyl, alkoxy, aryloxy, nitro, alkyl- or aryl-ureido and alkyl- or aryl-carbamoyl groups, any of which may be further substituted. Preferred groups are halogen, cyano, alkoxycarbonyl, alkylsulfamoyl, alkyl-sulfonamido, alkylsulfonyl, carbamoyl, alkylcarbamoyl or alkylcarbonamido. Suitably, Rxe2x80x3 is a 4-chlorophenyl, 3,4-dichlorophenyl, 3,4-difluorophenyl, 4-cyanophenyl, 3-chloro-4-cyanophenyl, pentafluorophenyl, or a 3- or 4-sulfonamidophenyl group.
In formula (I), when Rxe2x80x2xe2x80x3 is alkyl it may be unsubstituted or substituted with a substituent such as halogen or alkoxy. When Rxe2x80x2xe2x80x3 is aryl or a heterocycle, it may be substituted. Desirably it is not substituted in the position alpha to the sulfonyl group.
In formula (I), when Rxe2x80x2xe2x80x3 is a phenyl group, it may be substituted in the meta and/or para positions with one to three substituents independently selected from the group consisting of halogen, and unsubstituted or substituted alkyl, alkoxy, aryloxy, acyloxy, acylamino, alkyl- or aryl-sulfonyloxy, alkyl- or aryl-sulfamoyl, alkyl- or aryl-sulfamoylamino, alkyl- or aryl-sulfonamido, alkyl- or aryl-ureido, alkyl- or aryl-oxycarbonyl, alkyl- or aryl-oxy-carbonylamino and alkyl- or aryl-carbamoyl groups.
In particular, each substituent may be an alkyl group such as methyl, t-butyl, heptyl, dodecyl, pentadecyl, octadecyl or 1,1,2,2-tetramethylpropyl; an alkoxy group such as methoxy, t-butoxy, octyloxy, dodecyloxy, tetradecyloxy, hexadecyloxy or octadecyloxy; an aryloxy group such as phenoxy, 4-t-butylphenoxy or 4-dodecyl-phenoxy; an alkyl- or aryl-acyloxy group such as acetoxy or dodecanoyloxy; an alkyl- or aryl-acylamino group such as acetamido, hexadecanamido or benzamido; an alkyl- or aryl-sulfonyloxy group such as methyl-sulfonyloxy, dodecylsulfonyloxy or 4-methylphenyl-sulfonyloxy; an alkyl- or aryl-sulfamoyl-group such as N-butylsulfamoyl or N-4-t-butylphenylsulfamoyl; an alkyl- or aryl-sulfamoylamino group such as N-butyl-sulfamoylamino or N-4-t-butylphenylsulfamoyl-amino; an alkyl- or aryl-sulfonamido group such as methane-sulfonamido, hexadecanesulfonamido or 4-chlorophenyl-sulfonamido; an alkyl- or aryl-ureido group such as methylureido or phenylureido; an alkoxy- or aryloxy-carbonyl such as methoxycarbonyl or phenoxycarbonyl; an alkoxy- or aryloxy-carbonylamino group such as methoxy-carbonylamino or phenoxycarbonylamino; an alkyl- or aryl-carbamoyl group such as N-butylcarbamoyl or N-methyl-N-dodecylcarbamoyl; or a perfluoroalkyl group such as trifluoromethyl or heptafluoropropyl.
Suitably the above substituent groups have 1 to 30 carbon atoms, more preferably 8 to 20 aliphatic carbon atoms. A desirable substituent is an alkyl group of 12 to 18 aliphatic carbon atoms such as dodecyl, pentadecyl or octadecyl or an alkoxy group with 8 to 18 aliphatic carbon atoms such as dodecyloxy and hexadecyloxy or a halogen such as a meta or para chloro group, carboxy or sulfonamido. Any such groups may contain interrupting heteroatoms such as oxygen to form e.g. polyalkylene oxides.
In formula (I) or (IA) Z is a hydrogen atom or a group which can be split off by the reaction of the coupler with an oxidized color developing agent, known in the photographic art as a xe2x80x98coupling-off groupxe2x80x99 and may preferably be hydrogen, chloro, fluoro, substituted aryloxy or mercaptotetrazole, more preferably hydrogen or chloro.
The presence or absence of such groups determines the chemical equivalency of the coupler, i.e., whether it is a 2-equivalent or 4-equivalent coupler, and its particular identity can modify the reactivity of the coupler. Such groups can advantageously affect the layer in which the coupler is coated, or other layers in the photographic recording material, by performing, after release from the coupler, functions such as dye formation, dye hue adjustment, development acceleration or inhibition, bleach acceleration or inhibition, electron transfer facilitation, color correction, and the like.
Representative classes of such coupling-off groups include, for example, halogen, alkoxy, aryloxy, heterocyclyloxy, sulfonyloxy, acyloxy, acyl, heterocyclylsulfonamido, heterocyclylthio, benzothiazolyl, phosophonyloxy, alkylthio, arylthio, and arylazo. These coupling-off groups are described in the art, for example, in U.S. Pat. Nos. 2,455,169; 3,227,551; 3,432,521; 3,467,563; 3,617,291; 3,880,661; 4,052,212; and 4,134,766; and in U.K. Patent Nos. and published applications 1,466,728; 1,531,927; 1,533,039; 2,066,755A, and 2,017,704A. Halogen, alkoxy and aryloxy groups are most suitable.
Examples of specific coupling-off groups are xe2x80x94Cl, xe2x80x94F, xe2x80x94Br, xe2x80x94SCN, xe2x80x94OCH3, xe2x80x94OC6H5, xe2x80x94OCH2C(xe2x95x90O)NHCH2CH2OH, xe2x80x94OCH2C(O)NHCH2CH2OCH3, xe2x80x94OCH2C(O)NHCH2CH2OC(xe2x95x90O)OCH3, xe2x80x94P(xe2x95x90O)(OC2H5)2, xe2x80x94SCH2CH2COOH,
Typically, the coupling-off group is a chlorine atom, hydrogen atom or p-methoxyphenoxy group.
It is essential that the substituent groups be selected so as to adequately ballast the coupler and the resulting dye in the organic solvent in which the coupler is dispersed. The ballasting may be accomplished by providing hydrophobic substituent groups in one or more of the substituent groups. Generally a ballast group is an organic radical of such size and configuration as to confer on the coupler molecule sufficient bulk and aqueous insolubility as to render the coupler substantially nondiffusible from the layer in which it is coated in a photographic element. Thus the combination of substituent are suitably chosen to meet these criteria. To be effective, the ballast will usually contain at least 8 carbon atoms and typically contains 10 to 30 carbon atoms. Suitable ballasting may also be accomplished by providing a plurality of groups which in combination meet these criteria. In the preferred embodiments of the invention R1 in formula (I) is a small alkyl group or hydrogen. Therefore, in these embodiments the ballast would be primarily located as part of the other groups. Furthermore, even if the coupling-off group Z contains a ballast it is often necessary to ballast the other substituents as well, since Z is eliminated from the molecule upon coupling; thus, the ballast is most advantageously provided as part of groups other than Z.
The following examples further illustrate preferred coupler of the invention. It is not to be construed that the present invention is limited to these
Preferred couplers are IC-3, IC-7, IC-35, and IC-36 because of their suitably narrow left bandwidths.
Couplers that form magenta dyes upon reaction with oxidized color developing agent are described in such representative patents and publications as: U.S. Pat. Nos. 2,311,082; 2,343,703; 2,369,489; 2,600,788; 2,908,573; 3,062,653; 3,152,896; 3,519,429; 3,758,309; and xe2x80x9cFarbkuppler-eine Literature Ubersicht, xe2x80x9d published in Agfa Mitteilungen, Band III, pp. 126-156 (1961). Preferably such couplers are pyrazolones, pyrazolotriazoles, or pyrazolobenzimidazoles that form magenta dyes upon reaction with oxidized color developing agents. Especially preferred couplers are 1H-pyrazolo [5,1-c]-1,2,4-triazole and 1H-pyrazolo [1,5-b]-1,2,4-triazole. Examples of 1H-pyrazolo [5,1-c]-1,2,4-triazole couplers are described in U.K. Patent Nos. 1,247,493; 1,252,418; 1,398,979; U.S. Pat. Nos. 4,443,536; 4,514,490; 4,540,654; 4,590,153; 4,665,015; 4,822,730; 4,945,034; 5,017,465; and 5,023,170. Examples of 1H-pyrazolo [1,5-b]-1,2,4-triazoles can be found in European Patent applications 176,804; 177,765; U.S. Pat. Nos. 4,659,652; 5,066,575; and 5,250,400.
Typical pyrazoloazole and pyrazolone couplers are represented by the following formulas:
wherein Ra and Rb independently represent H or a substituent; Rc is a substituent (preferably an aryl group); Rd is a substituent (preferably an anilino, carbonamido, ureido, carbamoyl, alkoxy, aryloxycarbonyl, alkoxycarbonyl, or N-heterocyclic group); X is hydrogen or a coupling-off group; and Za, Zb, and Zc are independently a substituted methine group, xe2x95x90Nxe2x80x94, xe2x95x90Cxe2x80x94, or xe2x80x94NHxe2x80x94, provided that one of either the Zaxe2x80x94Zb bond or the Zbxe2x80x94Zc bond is a double bond and the other is a single bond, and when the Zbxe2x80x94Zc bond is a carbon-carbon double bond, it may form part of an aromatic ring, and at least one of Za, Zb, and Zc represents a methine group connected to the group Rb.
Specific examples of such couplers are:
Couplers that form yellow dyes upon reaction with oxidized color developing agent are described in such representative patents and publications as: U.S. Pat. Nos. 2,298,443; 2,407,210; 2,875,057; 3,048,194; 3,265,506; 3,447,928; 3,960,570; 4,022,620; 4,443,536; 4,910,126; and 5,340,703 and xe2x80x9cFarbkuppler-eine Literature Ubersicht,xe2x80x9d published in Agfa Mitteilungen, Band III, pp. 112-126 (1961). Such couplers are typically open chain ketomethylene compounds. Also preferred are yellow couplers such as described in, for example, European Patent Application Nos. 482,552; 510,535; 524,540; 543,367; and U.S. Pat. No. 5,238,803. For improved color reproduction, couplers which give yellow dyes that cut off sharply on the long wavelength side are particularly preferred (for example, see U.S. Pat. No. 5,360,713).
Typical preferred yellow couplers are represented by the following formulas:
wherein R1, R2, Q1 and Q2 each represents a substituent; X is hydrogen or a coupling-off group; Y represents an aryl group or a heterocyclic group; Q3 represents an organic residue required to form a nitrogen-containing heterocyclic group together with the  greater than Nxe2x80x94; and Q4 represents nonmetallic atoms necessary to from a 3- to 5-membered hydrocarbon ring or a 3- to 5-membered heterocyclic ring which contains at least one hetero atom selected from N, O, S, and P in the ring. Particularly preferred is when Q1 and Q2 each represents an alkyl group, an aryl group, or a heterocyclic group, and R2 represents an aryl or tertiary alkyl group.
Preferred yellow couplers can be of the following general structures
Unless otherwise specifically stated, substituent groups which may be substituted on molecules herein include any groups, whether substituted or unsubstituted, which do not destroy properties necessary for photographic utility. When the term xe2x80x9cgroupxe2x80x9d is applied to the identification of a substituent containing a substitutable hydrogen, it is intended to encompass not only the substituent""s unsubstituted form, but also its form further substituted with any group or groups as herein mentioned. Suitably, the group may be halogen or may be bonded to the remainder of the molecule by an atom of carbon, silicon, oxygen, nitrogen, phosphorous, or sulfur. The substituent may be, for example, halogen, such as chlorine, bromine or fluorine; nitro; hydroxyl; cyano; carboxyl; or groups which may be further substituted, such as alkyl, including straight or branched chain alkyl, such as methyl, trifluoromethyl, ethyl, t-butyl, 3-(2,4-di-t-pentylphenoxy) propyl, and tetradecyl; alkenyl, such as ethylene, 2-butene; alkoxy, such as methoxy, ethoxy, propoxy, butoxy, 2-methoxyethoxy, sec-butoxy, hexyloxy, 2-ethylhexyloxy, tetradecyloxy, 2-(2,4-di-t-pentylphenoxy)ethoxy, and 2-dodecyloxyethoxy; aryl such as phenyl, 4-t-butylphenyl, 2,4,6-trimethylphenyl, naphthyl; aryloxy, such as phenoxy, 2-methylphenoxy, alpha- or beta-naphthyloxy, and 4-tolyloxy; carbonamido, such as acetamido, benzamido, butyramido, tetradecanamido, alpha-(2,4-di-t-pentyl-phenoxy)acetamido, alpha-(2,4-di-t-pentylphenoxy)butyramido, alpha-(3-pentadecylphenoxy)-hexanamido, alpha-(4-hydroxy-3-t-butylphenoxy)-tetradecanamido, 2-oxo-pyrrolidin-1-yl, 2-oxo-5-tetradecylpyrrolin-1-yl, N-methyltetradecanamido, N-succinimido, N-phthalimido, 2,5-dioxo-1-oxazolidinyl, 3-dodecyl-2,5-dioxo-1-imidazolyl, and N-acetyl-N-dodecylamino, ethoxycarbonylamino, phenoxycarbonylamino, benzyloxycarbonylamino, hexadecyloxycarbonylamino, 2,4-di-t-butylphenoxycarbonylamino, phenylcarbonylamino, 2,5-(di-t-pentylphenyl)carbonylamino, p-dodecyl-phenylcarbonylamino, p-toluylcarbonylamino, N-methylureido, N,N-dimethylureido, N-methyl-N-dodecylureido, N-hexadecylureido, N,N-dioctadecylureido, N,N-dioctyl-Nxe2x80x2-ethylureido, N-phenylureido, N,N-diphenylureido, N-phenyl-N-p-toluylureido, N-(m-hexadecylphenyl)ureido, N,N-(2,5-di-t-pentylphenyl)-Nxe2x80x2-ethylureido, and t-butylcarbonamido; sulfonamido, such as methylsulfonamido, benzenesulfonamido, p-toluylsulfonamido, p-dodecylbenzenesulfonamido, N-methyltetradecylsulfonamido, N,N-dipropyl-sulfamoylamino, and hexadecylsulfonamido; sulfamoyl, such as N-methylsulfamoyl, N-ethylsulfamoyl, N,N-dipropylsulfamoyl, N-hexadecylsulfamoyl, N,N-dimethylsulfamoyl; N-[3-(dodecyloxy)propyl]sulfamoyl, N-[4-(2,4-di-t-pentylphenoxy)butyl]sulfamoyl, N-methyl-N-tetradecylsulfamoyl, and N-dodecylsulfamoyl; carbamoyl, such as N-methylcarbamoyl, N,N-dibutylcarbamoyl, N-octadecylcarbamoyl, N-[4-(2,4-di-t-pentylphenoxy)butyl]carbamoyl, N-methyl-N-tetradecylcarbamoyl, and N,N-dioctylcarbamoyl; acyl, such as acetyl, (2,4-di-t-amylphenoxy)acetyl, phenoxycarbonyl, p-dodecyloxyphenoxycarbonyl, methoxycarbonyl, butoxycarbonyl, tetradecyloxycarbonyl, ethoxycarbonyl, benzyloxycarbonyl, 3-pentadecyloxycarbonyl, and dodecyloxycarbonyl; sulfonyl, such as methoxysulfonyl, octyloxysulfonyl, tetradecyloxysulfonyl, 2-ethylhexyloxysulfonyl, phenoxysulfonyl, 2,4-di-t-pentylphenoxysulfonyl, methylsulfonyl, octylsulfonyl, 2-ethylhexylsulfonyl, dodecylsulfonyl, hexadecylsulfonyl, phenylsulfonyl, 4-nonylphenylsulfonyl, and p-toluylsulfonyl; sulfonyloxy, such as dodecylsulfonyloxy, and hexadecylsulfonyloxy; sulfinyl, such as methylsulfinyl, octylsulfmyl, 2-ethylhexylsulfinyl, dodecylsulfinyl, hexadecylsulfinyl, phenylsulfinyl, 4-nonylphenylsulfmyl, andp-toluylsulfinyl; thio, such as ethylthio, octylthio, benzylthio, tetradecylthio, 2-(2,4-di-t-pentylphenoxy)ethylthio, phenylthio, 2-butoxy-5-t-octylphenylthio, and p-tolylthio; acyloxy, such as acetyloxy, benzoyloxy, octadecanoyloxy, p-dodecylamidobenzoyloxy, N-phenylcarbamoyloxy, N-ethylcarbamoyloxy, and cyclohexylcarbonyloxy; amino, such as phenylanilino, 2-chloroanilino, diethylamino, dodecylamino; imino, such as 1 (N-phenylimido)ethyl, N-succinimido or 3-benzylhydantoinyl; phosphate, such as dimethylphosphate and ethylbutylphosphate; phosphite, such as diethyl and dihexylphosphite; a heterocyclic group, a heterocyclic oxy group or a heterocyclic thio group, each of which may be substituted and which contain a 3 to 7 membered heterocyclic ring composed of carbon atoms and at least one hetero atom selected from the group consisting of oxygen, nitrogen and sulfur, such as 2-furyl, 2-thienyl, 2-benzimidazolyloxy or 2-benzothiazolyl; quaternary ammonium, such as triethylammonium; and silyloxy, such as trimethylsilyloxy.
If desired, the substituents may themselves be further substituted one or more times with the described substituent groups. The particular substituents used may be selected by those skilled in the art to attain the desired photographic properties for a specific application and can include, for example, hydrophobic groups, solubilizing groups, blocking groups, releasing or releasable groups, etc. Generally, the above groups and substituents thereof may include those having up to 48 carbon atoms, typically 1 to 36 carbon atoms and usually less than 24 carbon atoms, but greater numbers are possible depending on the particular substituents selected.
Representative substituents on ballast groups include alkyl, aryl, alkoxy, aryloxy, alkylthio, hydroxy, halogen, alkoxycarbonyl, aryloxcarbonyl, carboxy, acyl, acyloxy, amino, anilino, carbonamido, carbamoyl, alkylsulfonyl, arylsulfonyl, sulfonamido, and sulfamoyl groups wherein the substituents typically contain 1 to 42 carbon atoms. Such substituents can also be further substituted.
Silver halide imaging layers substantially free of stabilizers are preferred. Silver halide stabilizers are typically utilized to protect from the growth of fog in storage and to reduce image fading. Stabilizers are however expensive and not generally required for silver halide images attached to packages of the invention since the shelf life of a package tends to be less than one calendar year. Silver halide imaging layers substantially free of stabilizers would be low in cost and have acceptable image quality for images attached to packages.
Stabilizers and scavengers that can be used in these photographic elements, but are not limited to, the following.
Examples of solvents which may be used in the invention include the following:
The dispersions used in photographic elements may also include ultraviolet (UV) stabilizers and so-called liquid UV stabilizers such as described in U.S. Pat. Nos. 4,992,358; 4,975,360; and 4,587,346. Examples of UV stabilizers are shown below.
The aqueous phase may include surfactants. Surfactant may be cationic, anionic, zwitterionic or non-ionic Useful surfactants include, but are not limited to, the following.
Further, it is contemplated to stabilize photographic dispersions prone to particle growth through the use of hydrophobic, photographically inert compounds such as disclosed by Zengerle et al in U.S. Pat. No. 5,468,604.
In a preferred embodiment the invention employs recording elements which are constructed to contain at least three silver halide emulsion layer units. A suitable full color, multilayer format for a recording element used in the invention is represented by Structure I.
wherein the red-sensitized, cyan dye image-forming silver halide emulsion unit is situated nearest the support; next in order is the green-sensitized, magenta dye image-forming unit, followed by the uppermost blue-sensitized, yellow dye image-forming unit. The image-forming units are separated from each other by hydrophilic colloid interlayers containing an oxidized developing agent scavenger to prevent color contamination. Silver halide emulsions satisfying the grain and gelatino-peptizer requirements described above can be present in any one or combination of the emulsion layer units. Additional useful multicolor, multilayer formats for an element of the invention include structures as described in U.S. Pat. No. 5,783,373. Each of such structures in accordance with the invention preferably would contain at least three silver halide emulsions comprised of high chloride grains (greater than 95% chloride) having at least 50 percent of their surface area bounded by {100} crystal faces and containing dopants from classes (i) and (ii), as described above. Preferably each of the emulsion layer units contains emulsion satisfying these criteria.
Conventional features that can be incorporated into multilayer (and particularly multicolor) recording elements contemplated for use in the method of the invention are illustrated by Research Disclosure, Item 38957, cited above:
XI. Layers and layer arrangements
XII. Features applicable only to color negative
XIII. Features applicable only to color positive
B. Color reversal
C. Color positives derived from color negatives
XIV. Scan facilitating features.
The recording elements comprising the radiation sensitive high chloride emulsion layers according to this invention can be conventionally optically printed, or in accordance with a particular embodiment of the invention can be image-wise exposed in a pixel-by-pixel mode using suitable high energy radiation sources typically employed in electronic printing methods. Suitable actinic forms of energy encompass the ultraviolet, visible and infrared regions of the electromagnetic spectrum as well as electron-beam radiation and is conveniently supplied by beams from one or more light emitting diodes or lasers, including gaseous or solid state lasers. Exposures can be monochromatic, orthochromatic or panchromatic. For example, when the recording element is a multilayer multicolor element, exposure can be provided by laser or light emitting diode beams of appropriate spectral radiation, for example, infrared, red, green or blue wavelengths, to which such element is sensitive. Multicolor elements can be employed which produce cyan, magenta, and yellow dyes as a function of exposure in separate portions of the electromagnetic spectrum, including at least two portions of the infrared region, as disclosed in the previously mentioned U.S. Pat. No. 4,619,892. Suitable exposures include those up to 2000 nm, preferably up to 1500 nm. Suitable light emitting diodes and commercially available laser sources are known and commercially available. Imagewise exposures at ambient, elevated or reduced temperatures and/or pressures can be employed within the useful response range of the recording element determined by conventional sensitometric techniques, as illustrated by T. H. James, The Theory of the Photographic Process, 4th Ed., Macmillan, 1977, Chapters 4, 6, 17, 18, and 23.
It has been observed that anionic [MXxYyL2] hexacoordination complexes, where M is a group 8 or 9 metal (preferably iron, ruthenium or iridium), X is halide or pseudohalide (preferably Cl, Br or CN) x is 3 to 5, Y is H2O, y is 0 or 1, L is a Cxe2x80x94C, Hxe2x80x94C or Cxe2x80x94Nxe2x80x94H organic ligand, and Z is 1 or 2, are surprisingly effective in reducing high intensity reciprocity failure (HIRF), low intensity reciprocity failure (LIRF) and thermal sensitivity variance and in in improving latent image keeping (LIK). As herein employed HIRF is a measure of the variance of photographic properties for equal exposures, but with exposure times ranging from 10xe2x88x921 to 10xe2x88x926 second. LIRF is a measure of the variance of photographic properties for equal exposures, but with exposure times ranging from 10xe2x88x921 to 100 seconds. Although these advantages can be generally compatible with face centered cubic lattice grain structures, the most striking improvements have been observed in high ( greater than 50 mole %, preferably  greater than 90 mole %) chloride emulsions. Preferred Cxe2x80x94C, Hxe2x80x94C or Cxe2x80x94Nxe2x80x94H organic ligands are aromatic heterocycles of the type described in U.S. Pat. No. 5,462,849. The most effective Cxe2x80x94C, Hxe2x80x94C or Cxe2x80x94Nxe2x80x94H organic ligands are azoles and azines, either unsubstituted or containing alkyl, alkoxy or halide substituents, where the alkyl moieties contain from 1 to 8 carbon atoms. Particularly preferred azoles and azines include thiazoles, thiazolines and pyrazines.
The quantity or level of high energy actinic radiation provided to the recording medium by the exposure source is generally at least 10xe2x88x924 ergs/cm2, typically in the range of about 10xe2x88x924 ergs/cm2 to 10xe2x88x923 ergs/cm2 and often from 10xe2x88x923 ergs/cm2 to 102 ergs/cm2. Exposure of the recording element in a pixel-by-pixel mode as known in the prior art persists for only a very short duration or time. Typical maximum exposure times are up to 100 xcexcseconds, often up to 10 xcexcseconds, and frequently up to only 0.5 xcexcseconds. Single or multiple exposures of each pixel are contemplated. The pixel density is subject to wide variation, as is obvious to those skilled in the art. The higher the pixel density, the sharper the images can be, but at the expense of equipment complexity. In general, pixel densities used in conventional electronic printing methods of the type described herein do not exceed 107 pixels/cm2 and are typically in the range of about 104 to 106 pixels/cm2. An assessment of the technology of high-quality, continuous-tone, color electronic printing using silver halide photographic paper which discusses various features and components of the system, including exposure source, exposure time, exposure level and pixel density and other recording element characteristics is provided in Firth et al., A Continuous-Tone Laser Color Printer, Journal of Imaging Technology, Vol. 14, No. 3, June 1988. As previously indicated herein, a description of some of the details of conventional electronic printing methods comprising scanning a recording element with high energy beams such as light emitting diodes or laser beams, are set forth in Hioki U.S. Pat. No. 5,126,235, European Patent Applications 479 167 A1 and 502 508 A1.
Once imagewise exposed, the recording elements can be processed in any convenient conventional manner to obtain a viewable image. Such processing is illustrated by Research Disclosure, Item 38957, cited above:
XVIII. Chemical development systems
XIX. Development
XX. Desilvering, washing, rinsing and stabilizing
In addition, a useful developer for the inventive material is a homogeneous, single part developing agent. The homogeneous, single-part color developing concentrate is prepared using a critical sequence of steps:
In the first step, an aqueous solution of a suitable color developing agent is prepared. This color developing agent is generally in the form of a sulfate salt. Other components of the solution can include an antioxidant for the color developing agent, a suitable number of alkali metal ions (in an at least stoichiometric proportion to the sulfate ions) provided by an alkali metal base, and a photographically inactive water-miscible or water-soluble hydroxy-containing organic solvent. This solvent is present in the final concentrate at a concentration such that the weight ratio of water to the organic solvent is from about 15:85 to about 50:50.
In this environment, especially at high alkalinity, alkali metal ions and sulfate ions form a sulfate salt that is precipitated in the presence of the hydroxy-containing organic solvent. The precipitated sulfate salt can then be readily removed using any suitable liquid/solid phase separation technique (including filtration, centrifugation or decantation). If the antioxidant is a liquid organic compound, two phases may be formed and the precipitate may be removed by discarding the aqueous phase.
The color developing concentrates of this invention include one or more color developing agents that are well known in the art that, in oxidized form, will react with dye forming color couplers in the processed materials. Such color developing agents include, but are not limited to, aminophenols, p-phenylenediamines (especially N,N-dialkyl-p-phenylenediamines) and others which are well known in the art, such as EP 0 434 097A1 (published Jun. 26, 1991) and EP 0 530 921A1 (published Mar. 10, 1993). It may be useful for the color developing agents to have one or more water-solubilizing groups as are known in the art. Further details of such materials are provided in Research Disclosure, publication 38957, pages 592-639 (September 1996). Research Disclosure is a publication of Kenneth Mason Publications Ltd., Dudley House, 12 North Street, Emsworth, Hampshire PO10 7DQ England (also available from Emsworth Design Inc., 121 West 19th Street, New York, N.Y. 10011). This reference will be referred to hereinafter as xe2x80x9cResearch Disclosurexe2x80x9d.
Preferred color developing agents include, but are not limited to, N,N-diethyl p-phenylenediamine sulfate (KODAK Color Developing Agent CD-2), 4-amino-3-methyl-N-(2-methane sulfonamidoethyl)aniline sulfate, 4-(N-ethyl-N-p-hydroxyethylamino)-2-methylaniline sulfate (KODAK Color Developing Agent CD-4), p-hydroxyethylethylaminoaniline sulfate, 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate (KODAK Color Developing Agent CD-3), 4-(N-ethyl-N-2-methanesulfonylaminoethyl)-2-methylphenylenediamine sesquisulfate, and others readily apparent to one skilled in the art.
In order to protect the color developing agents from oxidation, one or more antioxidants are generally included in the color developing compositions. Either inorganic or organic antioxidants can be used. Many classes of useful antioxidants are known, including but not limited to, sulfites (such as sodium sulfite, potassium sulfite, sodium bisulfite and potassium metabisulfite), hydroxylamine (and derivatives thereof), hydrazines, hydrazides, amino acids, ascorbic acid (and derivatives thereof), hydroxamic acids, aminoketones, mono- and polysaccharides, mono- and polyamines, quaternary ammonium salts, nitroxy radicals, alcohols, and oximes. Also useful as antioxidants are 1,4-cyclohexadines. Mixtures of compounds from the same or different classes of antioxidants can also be used if desired.
Especially useful antioxidants are hydroxylamine derivatives as described for example, in U.S. Pat. Nos. 4,892,804; 4,876,174; 5,354,646; 5,660,974, and 5,646,327 (Burns et al). Many of these antioxidants are mono- and dialkyihydroxylamines having one or more substituents on one or both alkyl groups. Particularly useful alkyl substituents include sulfo, carboxy, amino, sulfonamido, carbonamido, hydroxy and other solubilizing substituents.
More preferably, the noted hydroxylamine derivatives can be mono- or dialkylhydroxylamines having one or more hydroxy substituents on the one or more alkyl groups. Representative compounds of this type are described for example in U.S. Pat. No. 5,709,982 (Marrese et al) as having the structure I:
wherein R is hydrogen, a substituted or unsubstituted alkyl group of 1 to 10 carbon atoms, a substituted or unsubstituted hydroxyalkyl group of 1 to 10 carbon atoms, a substituted or unsubstituted cycloalkyl group of 5 to 10 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 10 carbon atoms in the aromatic nucleus.
X1 is xe2x80x94CR2(OH)CHR1xe2x80x94 and X2 is xe2x80x94CHR1CR2(OH)xe2x80x94 wherein R1 and R2 are independently hydrogen, hydroxy, a substituted or unsubstituted alkyl group or 1 or 2 carbon atoms, a substituted or unsubstituted hydroxyalkyl group of 1 or 2 carbon atoms, or R1 and R2 together represent the carbon atoms necessary to complete a substituted or unsubstituted 5- to 8-membered saturated or unsaturated carbocyclic ring structure.
Y is a substituted or unsubstituted alkylene group having at least 4 carbon atoms, and has an even number of carbon atoms, or Y is a substituted or unsubstituted divalent aliphatic group having an even total number of carbon and oxygen atoms in the chain, provided that the aliphatic group has a least 4 atoms in the chain.
Also in Structure I, m, n and p are independently 0 or 1. Preferably, each of m and n is 1, and p is 0.
Specific di-substituted hydroxylamine antioxidants include, but are not limited to: N,N-bis(2,3-dihydroxypropyl)hydroxylamine, N,N-bis(2-methyl-2,3-dihydroxypropyl)hydroxylamine and N,N-bis(1-hydroxymethyl-2-hydroxy-3-phenylpropyl)hydroxylamine. The first compound is preferred.
The colorants can be incorporated into the imaging element by direct addition of the colorant to a coating melt by mixing the colorant with an aqueous medium containing gelatin (or other hydrophilic colloid) at a temperature of 40xc2x0 C. or higher. The colorant can also be mixed with an aqueous solution of a water-soluble or water-dispersible surfactant or polymer, and passing the premix through a mill until the desired particle size is obtained. The mill can be any high energy device such as a colloid mill, high pressure homogenizer, or the like.
The preferred color of the pigment is blue as a blue pigment incorporated into a gelatin layer offsets the native yellowness of the gelatin yielding a neutral background for the image layers.
Suitable pigments used in this invention can be any inorganic or organic, colored materials which are practically insoluble in the medium in which they are incorporated. The preferred pigments are organic, and are those described in Industrial Organic Pigments: Production, Properties, Applications by W. Herbst and K. Hunger, 1993, Wiley Publishers. These include: Azo Pigments such as monoazo yellow and orange, diazo, naphthol, naphthol reds, azo lakes, benzimidazolone, disazo condensation, metal complex, isoindolinone and isoindoline, Polycyclic Pigments such as phthalocyanine, quinacridone, perylene, perinone, diketopyrrolo pyrrole and thioindigo, and Anthraquinone Pigments such as anthrapyrimidine, flavanthrone, pyranthrone, anthanthrone, dioxazine, triarylcarbodium and quinophthalone.
The most preferred pigments are the anthraquinones such as Pigment Blue 60, phthalocyanines such as Pigment Blue 15, 15:1, 15:3, 15:4 and 15:6, and quinacridones such as Pigment Red 122, as listed in NPIRI Raw Materials Data Handbook, Vol.. 4, Pigments, 1983, National Printing Research Institute. These pigments have a dye hue sufficient to overcome the native yellowness of the gelatin imaging layer and are easily dispersed in a aqueous solution.
An aqueous dispersion of the pigments is preferred because the preferred pigments are insoluble in most, if not all, organic solvents and, therefore, a high quality dispersion is not likely in a solvent system. In fact, the only solvent that will dissolve preferred pigments PR-122 and PB-15 is concentrated sulfuric acid, which is not an organic solvent. Preferred pigments of the invention are by nature, insoluble, crystalline solids, which is the most thermodynamically stable form that they can assume. In an oil and water dispersion, they would be in the form of an amorphous solid, which is thermodynamically unstable. Therefore, one would have to worry about the pigment eventually converting to the crystalline form with age. We might as well start with a crystalline solid and not worry about preventing the phase transition. Another reason to avoid solvent pigment dispersions is that the high boiling solvent is not removed with evaporation, and it could cause unwanted interactions in the coating melt such as ripening of DOH dispersion particles, or equilibration with other layers, if it was used in the coating. The use of solid particle dispersion avoids organic solvents altogether.
In the preferred embodiment, the colorant is dispersed in the binder in the form of a solid particle dispersion. Such dispersions are formed by first mixing the colorant with an aqueous solution containing a water-soluble or water-dispersible surfactant or polymer to form a coarse aqueous premix, and adding the premix to a mill. The amount of water-soluble or water-dispersible surfactant or polymer can vary over a wide range, but is generally in the range of 0.01% to 100% by weight of polymer, preferably about 0.3% to about 60%, and more preferably 0.5% to 50%, the percentages being by weight of polymer, based on the weight of the colorant useful in imaging.
The mill can be, for example, a ball mill, media mill, attritor mill, vibratory mill, or the like. The mill is charged with the appropriate milling media such as, for example, beads of silica, silicon nitride, sand, zirconium oxide, yttria-stabilized zirconium oxide, alumina, titanium, glass, polystyrene, etc. The bead sizes typically range from 0.25 to 3.0 mm in diameter, but smaller media can be used if desired. The premix is milled until the desired particle size range is reached.
The solid colorant particles are subjected to repeated collisions with the milling media, resulting in crystal fracture, deagglomeration, and consequent particle size reduction. The solid particle dispersions of the colorant should have a final average particle size of less than 1 xcexcm, preferably less than 0.1 micrometers, and most preferably between 0.01 and 0.1 xcexcm. Most preferably, the solid colorant particles are of sub-micrometer average size. Solid particle size between 0.01 and 0.1 provides the best pigment utilization and had a reduction in unwanted light absorption compared to pigments with a particle size greater than 1.2 xcexcm.
The preferred gelatin to pigment ratio in any gelatin layer is between 65,000:1 to 195,000:1. This gelatin to pigment ratio is preferred as this range provides the necessary color correction to typical photographic imaging layers and typical ink jet dye receiving layers to provide a perceptually preferred neutral background in the image. The preferred coverage of pigment in the gelatin layer is between 0.006 grams/m2 and 0.020 grams/m2. Coverages less than 0.006 granm/m2 are not sufficient to provide proper correction of the color and coverages greater than 0.025 grams/m2 yield a density minimum that has been found to be objectionable by consumers.
Surfactants, polymers, and other additional conventional addenda may also be used in the dispersing process described herein in accordance with prior art solid particle dispersing procedures. Such surfactants, polymers and other addenda are disclosed in U.S. Pat. Nos. 5,468,598; 5,300,394; 5,278,037; 4,006,025; 4,924,916; 4,294,917; 4,940,654; 4,950,586; 4,927,744; 5,279,931; 5,158,863; 5,135,844; 5,091,296; 5,089,380; 5,103,640; 4,990,431; 4,970,139; 5,256,527; 5,089,380; 5,103,640; 4,990,431; 4,970,139; 5,256,527; 5,015,564; 5,008,179; 4,957,857; and 2,870,012, and British Patent specifications Nos. 1,570,362 and 1,131,179 in the dispersing process of the colorants.
Additional surfactants or other water soluble polymers may be added after formation of the colorant dispersion, before or after subsequent addition of the colorant dispersion to an aqueous coating medium for coating onto an imaging element support. The aqueous medium preferably contains other compounds such as stabilizers and dispersants, for example, additional anionic, nonionic, zwitterionic, or cationic surfactants, and water soluble binders such as gelatin as is well known in the imaging art. The aqueous coating medium may further contain other dispersions or emulsions of compounds useful in imaging.

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